- Conference of the Parties 15 – Copenhagen Accord – United Nations Framwork Convention on Climate Change – 18/12/2009 – http://unfccc.int/home/items/5262.php
“To achieve the ultimate objective of the Convention to stabilize greenhouse gas concentration in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system, we shall, recognizing the scientific view that the increase in global temperature should be below 2 degrees Celsius, on the basis of equity and in the context of sustainable development, enhance our long-term cooperative action to combat climate change. We recognize the critical impacts of climate change and the potential impacts of response measures on countries particularly vulnerable to its adverse effects and stress the need to establish a comprehensive adaptation programme including international support.” - Joeri Rogelj et al (2010) – Copenhagen Accord pledges are paltry – Nature 464:1126-1128 doi:10.1038/4641126a – 21/04/2010 – Potsdam Institute for Climate Impact Research – 9 authors – Peer-reviewed
“Current national emissions targets can’t limit global warming to 2 °C … they might even lock the world into exceeding 3 °C warming.” - Gabriele C. Hegerl, Francis W. Zwiers et al (2007) – Chap. 8: Understanding and Attributing Climate Change – En: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Susan Solomon et al (eds.)] – Intergovernmental Panel on Climate Change – Peer-reviewed
«…only in the case of essentially complete elimination of emissions can the atmospheric concentration of CO2 ultimately be stabilised at a constant level. All other cases of moderate CO2 emission reductions show increasing concentrations because of the characteristic exchange processes associated with the cycling of carbon in the climate system….» - James Hansen et al (2008) – Target Atmospheric CO2: Where Should Humanity Aim? – The Open Atmospheric Science Journal 2:217-231 – 39479 – NASA Goddard Institute for Space Studies and Columbia University Earth Institute – 10 authors – Peer-reviewed
“If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that.” - Andrew A. Lacis et al (2010) – Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature – Science 330:356-359 doi:10.1126/science.1190653 – 14/10/2010 – NASA Goddard Institute for Space Studies – 4 authors – Peer-reviewed
«The continuing high rate of atmospheric CO2 increase is particularly worrisome, because the present CO2 level of 390 ppm is far in excess of the 280 ppm that is more typical for the interglacial maximum, and still the atmospheric CO2 control knob is now being turned faster than at any time in the geological record (20). The concern is that we are well past even the 300- to 350-ppm target level for atmospheric CO2, beyond which dangerous anthropogenic interference in the climate system would exceed the 25% risk tolerance for impending degradation of land and ocean ecosystems, sea-level rise, and inevitable disruption of socioeconomic and foodproducing infrastructure (21, 22). Furthermore, the atmospheric residence time of CO2 is exceedingly long, being measured in thousands of years (23). This makes the reduction and control of atmospheric CO2 a serious and pressing issue, worthy of real-time attention.» - M. Ha-Duong, M. J. Grubb and J.-C. Hourcade (1997) – Influence of socioeconomic inertia and uncertainty on optimal CO2-emission abatement – Nature 390:270-273 doi:10.1038/36825 – 24/10/1997 – Centre International de Recherche sur l’Environnement et le Développement, Energy and Environmental Programme, Royal Institute of International Affairs – Peer-reviewed
«We find that the ‘integrated assessment’ models previously applied to these issues under-represent inertia … We conclude that if there is a significant probability of having to maintain atmospheric greenhouse gas concentrations below about double those of the pre-industrial era, then the economic risks associated with deferring abatement justify starting to limit CO2 emissions from energy systems immediately.» - Kevin Anderson and Alice Bows (2008) – Reframing the climate change challenge in light of post-2000 emission trends – Philosophical Transactions of the Royal Society of London A doi:10.1098/rsta.2008.0138 – 13/11/2008 – Tyndall Centre for Climate Change Research, Mechanical, Civil and Aerospace Engineering, University of Manchester – Peer-reviewed
“It is increasingly unlikely any global agreement will deliver the radical reversal in emission trends required for stabilization at 450 ppmv carbon dioxide equivalent (CO2e). Similarly, the current framing of climate change cannot be reconciled with the rates of mitigation necessary to stabilize at 550 ppmv CO2e and even an optimistic interpretation suggests stabilization much below 650 ppmv CO2e is improbable.” - George Monbiot – If we behave as if it’s too late, then our prophecy is bound to come true – The Guardian – 17/03/2009 – http://www.guardian.co.uk/commentisfree/2009/mar/17/monbiot-copenhagen-emission-cuts
“Quietly in public, loudly in private, climate scientists everywhere are saying the same thing: it’s over. The years in which more than 2 ºC of global warming could have been prevented have passed, the opportunities squandered by denial and delay. On current trajectories we’ll be lucky to get away with 4 ºC. Mitigation (limiting greenhouse gas pollution) has failed; now we must adapt to what nature sends our way. If we can” - Nicholas Stern (2006) – Stern review on the economics of climate change – Cambridge University Press, Cambridge, UK – Grantham Institute, IndiaObservatory, and STICERD at the London School of Economics and Political Science
- Fiona Harvey and Jim Pickard – Stern takes bleaker view on warming – Financial Times – 16/04/2008 – http://www.ft.com/cms/s/d3e78456-0bde-11dd-9840-0000779fd2ac,Authorised=false.html
“The Stern report on climate change underestimated the risks of global warming, its author said on Wednesday, and should have presented a gloomier view of the future. “We underestimated the risks … we underestimated the damage associated with temperature increases … and we underestimated the probabilities of temperature increases,” Lord Stern, former chief economist at the World Bank, told the Financial Times on Wednesday.” - Richard B. Alley et al (2003) – Abrupt Climate Change – Science 299:2005-2010 – 28/03/2003 – Department of Geosciences and EMS Environment Institute, Pennsylvania State University – 11 authors – Peer-reviewed
“Large, abrupt, and widespread climate changes with major impacts have occurred repeatedly in the past, when the Earth system was forced across thresholds. Although abrupt climate changes can occur for many reasons, it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events. Were such an event to recur, the economic and ecological impacts could be large and potentially serious. Unpredictability exhibited near climate thresholds in simple models shows that some uncertainty will always be associated with projections. In light of these uncertainties, policy-makers should consider expanding research into abrupt climate change, improving monitoring systems, and taking actions designed to enhance the adaptability and resilience of ecosystems and economies.” - Philippe Ambrosi (2005) – Mind the rate! Why rate of global climate change matters, and how much – Centre International des Recherches sur l’Environement et le Développement – 01/09/2005
“Given this uncertainty, a 2 ºC could lead to rather stringent policy recommendations for the coming decades and might prove unacceptable. Furthermore, the uncertainty about climate sensitivity magnifies the influence of the rate constraint on short-term decision, leading to rather stringent policy recommendations for the coming decades.” - Jeffrey P. Severinghaus et al (1998) – Timing of abrupt climate change at the end of the Younger Dryas interval from thermally fractionated gases in polar ice – Nature 391:141-146 doi:10.1038/34346 – 08/01/1998 – Graduate School of Oceanography, University of Rhode Island – 5 authors – Peer-reviewed
“Ice-core studies that infer palaeotemperature from the ratio of oxygen isotopes in the ice1,2 and accumulation rate3 have suggested that Greenland temperatures rose in less than a decade at the climate transition marking the end of the Younger Dryas cold interval and the beginning of the warmer Holocene epoch at 11.6 kyr before present, BP (here ‘present’ indicates AD 1950). Abrupt changes of similar age have appeared in other climate records over much of the globe.” - Timothy M. Lenton et al (2008) – Tipping elements in the Earth’s climate system – Proceedings of the National Academy of Sciences PNAS 105:1786-1793 doi:10.1073/pnas.0705414105 – 12/02/2008 – School of Environmental Sciences, University of East Anglia + Tyndall Centre for Climate Change Research – 7 authors – Peer-reviewed
“Society may be lulled into a false sense of security by smooth projections of global change. Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change. The greatest threats are tipping the Arctic sea-ice and the Greenland ice sheet, and at least five other elements could surprise us by exhibiting a nearby tipping point. This knowledge should influence climate policy, but a full assessment of policy relevance would require that, for each potential tipping element, we answer the following questions: Mitigation: Can we stay clear of ρcrit? Adaptation: Can ^F be tolerated?” - Joel B. Smith et al (2009) – Assessing dangerous climate change through an update of the Intergovernmental Panel on Climate Change (IPCC) ‘reasons for concern’ – Proceedings of the National Academy of Sciences PNAS 106:4133–4137 doi:10.1073/pnas.0812355106 – 17/03/2009 – Stratus Consulting, Inc. – http://www.pnas.org/content/106/11/4133.full.pdf+html – 15 authors – Peer-reviewed
“Based on our expert judgment about new findings … compared with results reported in the TAR [IPCC Third Assessment Report], smaller increases in GMT [Global Mean Temperature] are now estimated to lead to significant or substantial consequences in the framework of the 5 ‘‘reasons for concern.’’ - Kevin Anderson and Alice Bows (2011) – Beyond ‘dangerous’ climate change: emission scenarios for a new world – Philosophical Transactions of the Royal Society of London A 369: :20-44 doi:10.1098/rsta.2010.0290 – Published online: 29/11/2010 – Tyndall Centre for Climate Change Research + School of Mechanical, Aerospace and Civil Engineering + School of Environmental Sciences and School of Development, University of East Anglia; Sustainable Consumption Institute, School of Earth, Atmospheric and Environmental Sciences, University of Manchester – Peer-reviewed
“The analysis suggests that despite high-level statements to the contrary, there is now little to no chance of maintaining the global mean surface temperature at or below 2◦C. Moreover, the impacts associated with 2◦C have been revised upwards, sufficiently so that 2◦C now more appropriately represents the threshold between ‘dangerous’ and ‘extremely dangerous’ climate change.” - Richard A. Betts et al (2011) – When could global warming reach 4°C? – Philosophical Transactions of the Royal Society of London A 369:67-84 doi:10.1098/rsta.2010.0292 – Published online: 29/11/2010 – Met Office Hadley Centre – 6 authors – Peer-reviewed
“Using these GCM projections along with simple climate-model projections, including uncertainties in carbon-cycle feedbacks, and also comparing against other model projections from the IPCC, our best estimate is that the A1FI emissions scenario would lead to a warming of 4◦C relative to pre-industrial during the 2070s. If carbon-cycle feedbacks are stronger, which appears less likely but still credible, then 4◦C warming could be reached by the early 2060s in projections that are consistent with the IPCC’s ‘likely range’.” - Gaia Vince – How to survive the coming century – New Scientist 2697 – 25/02/2009 – http://www.newscientist.com/article/mg20126971.700-how-to-survive-the-coming-century.html
“According to models, we could cook the planet by 4 °C by 2100. Some scientists fear that we may get there as soon as 2050. If this happens, the ramifications for life on Earth are so terrifying that many scientists contacted for this article preferred not to contemplate them (…)” - Jock Martin and Thomas Henrichs (2010) – State of the environment report – European Environment Agency doi:10.2800/45773 – 29/11/2010 – http://www.eea.europa.eu/soer/synthesis/synthesis
“For the Mediterranean basin, in particular, increasing mean temperatures and decreases in water availability are expected to exacerbate current vulnerability to droughts, forest fires and heat waves … Projections show significant reductions in summer soil moisture in the Mediterranean region, and increases in north-eastern Europe (6). Furthermore, prolonged drought periods due to climatic changes may contribute to soil degradation and increase the risk of desertification in parts of the Mediterranean and eastern Europe … Droughts are also associated with or lead to an increased soil erosion risk. Desertification is a problem in parts of the Mediterranean and central and eastern Europe … Water resource over-exploitation, combined with insufficient access to safe drinking water and sanitation, for example, are critical challenges both in Eastern Europe and the Mediterranean.” - Pete Harrison – Watchdog warns of higher Mediterranean temperatures – Reuters – 30/11/2010 – http://in.reuters.com/article/idINIndia-53238020101130
“Children born today in countries such as Spain and Italy will witness a 7 degrees Celsius rise in summer temperatures by the end of their lives, the European Union’s environment watchdog warned on Tuesday. Deaths due to heat shock will rise, southern crops such as grapes will be pushed northwards and flagship European plants such as Switzerland’s edelweiss will face extinction, the European Environment Agency (EEA) said.” - P. H. Gleick et al (2010) – Climate Change and the Integrity of Science – Science 328:689-690 doi:10.1126/science.328.5979.689 – 07/05/2010 – U.S. National Academy of Sciences – http://www.pacinst.org/climate/climate_statement.pdf – 255 authors– Peer-reviewed
«For instance, there is compelling scientific evidence that our planet is about 4.5bn years old (the theory of the origin of Earth), that our universe was born from a single event about 14bn years ago (the Big Bang theory), and that today’s organisms evolved from ones living in the past (the theory of evolution). Even as these are overwhelmingly accepted by the scientific community, fame still awaits anyone who could show these theories to be wrong. Climate change now falls into this category: there is compelling, comprehensive, and consistent objective evidence that humans are changing the climate in ways that threaten our societies and the ecosystems on which we depend. Many recent assaults on climate science and, more disturbingly, on climate scientists by climate change deniers, are typically driven by special interests or dogma, not by an honest effort to provide an alternative theory that credibly satisfies the evidence.» - Richard B. Alley (2009) – The Biggest Control Knob: Carbon Dioxide in Earth’s Climate History – American Geophysical Union Meeting 2009 – 16/12/2009 – Evan Pugh Professor, Department of Geosciences and Earth and Environmental Systems Institute, The Pennsylvania State University – http://www.agu.org/meetings/fm09/lectures/lecture_videos/A23A.shtml
- Andrew A. Lacis et al (2010) – Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature – Science 330:356-359 doi:10.1126/science.1190653 – 14/10/2010 – NASA Goddard Institute for Space Studies – 4 authors – Peer-reviewed
“Ample physical evidence shows that carbon dioxide (CO2) is the single most important climate-relevant greenhouse gas in Earth’s atmosphere. This is because CO2, like ozone, N2O, CH4, and chlorofluorocarbons, does not condense and precipitate from the atmosphere at current climate temperatures, whereas water vapor can and does. Noncondensing greenhouse gases, which account for 25% of the total terrestrial greenhouse effect, thus serve to provide the stable temperature structure that sustains the current levels of atmospheric water vapor and clouds via feedback processes that account for the remaining 75% of the greenhouse effect. Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state.” - Johan Rockström et al (2009) – Planetary Boundaries: Exploring the Safe Operating Space for Humanity – Ecology and Society 14:32-64 – 14/09/2009 – Stockholm Resilience Centre, Stockholm University, Stockholm Environment Institute – http://www.ecologyandsociety.org/vol14/iss2/art32/ – 29 authors – Peer-reviewed
“We have identified nine planetary boundaries and, drawing upon current scientific understanding, we propose quantifications for seven of them. These seven are climate change (CO2 concentration in the atmosphere <350 ppm and/or a maximum change of +1 W m-2 in radiative forcing); ocean acidification (mean surface seawater saturation state with respect to aragonite ³ 80% of pre-industrial levels); stratospheric ozone (<5% reduction in O3 concentration from pre-industrial level of 290 Dobson Units); biogeochemical nitrogen (N) cycle (limit industrial and agricultural fixation of N2 to 35 Tg N yr-1) and phosphorus (P) cycle (annual P inflow to oceans not to exceed 10 times the natural background weathering of P); global freshwater use (<4000 km3 yr-1 of consumptive use of runoff resources); land system change (<15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of <10 extinctions per million species). The two additional planetary boundaries for which we have not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading.” - Johan Rockström et al (2009) – A safe operating space for humanity – Nature 461:472-475 doi:10.1038/461472a – 23/09/2009 – Stockholm Resilience Centre, Stockholm University – Peer-reviewed
“Humanity may soon be approaching the boundaries for global freshwater use, change in land use, ocean acidification and interference with the global phosphorous cycle (see Fig. 1). Our analysis suggests that three of the Earth-system processes — climate change, rate of biodiversity loss and interference with the nitrogen cycle — have already transgressed their boundaries. For the latter two of these, the control variables are the rate of species loss and the rate at which N2 is removed from the atmosphere and converted to reactive nitrogen for human use, respectively. These are rates of change that cannot continue without significantly eroding the resilience of major components of Earth-system functioning. Here we describe these three processes.” - D.P. van Vuuren and A. Fabe (2009) – Growing within Limits. A Report to the Global Assembly 2009 of the Club of Rome – Netherlands Environmental Assessment Agency (PBL) – October 2009 – 128 pp – ISBN: 978-90-6960-234-9 – http://www.rivm.nl/bibliotheek/rapporten/500201001.pdf – Peer-reviewed
«Since the publication of ‘The Limits to Growth’ for the Club of Rome in 1972, it has become increasingly clear that the current trends in the consumption of fossil fuel and other resources, use of land, and pressure on the Earth’s capacity to deal with pollution lead to serious environmental risks. In numerous global environmental assessments published since 1972, more detailed analyses have been made in terms of analysis of specific environmental problems and their magnitude. These studies also show that should historic trends continue in the coming decades, then the world will run into an increasing range of environmental and social tensions (Figure). Two top priorities can be derived: 1. ensuring a sustainable energy supply while avoiding climate change, and 2. preventing terrestrial biodiversity losses while ensuring food security – also in light of possible threats to human development, including poverty.» - G. R. van der Werf et al (2009) – CO2 emissions from forest loss – Nature Geoscience 2:733-808 – November 2009 – Faculty of Earth and Life Sciences,VU University Amsterdam – 8 authors – Peer-reviewed
“The combined contribution of deforestation, forest degradation and peatland emissions to total anthropogenic CO2 emissions is about 15% (range 8–20%; see Supplementary Information for a comparison with all anthropogenic greenhouse gases). We conclude that taking into account carbon emissions from peatlands would enhance the effectiveness of REDD programmes, which are under discussion in the United Nation’s climate policy negotiations.” - IPCC. 2007. Summary for Policymakers. In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL, eds. Climate Change 2007: The Physical Sciences. Contribution of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press
- Daniel G. Boyce, Marlon R. Lewis and Boris Worm (2010) – Global phytoplankton decline over the past century – Nature 466:591–596 doi:10.1038/nature09268 – 29/07/2010 – Biology Department, Dalhousie University – Peer-reviewed
“Generating roughly half the planetary primary production (ref), marine phytoplankton affect the abundance and diversity of-marine organisms, drive marine ecosystem functioning, and set the upper limits to fishery yields (ref). Phytoplankton strongly influence climate processes (ref) and biogeochemical cycles (refs) particularly the carbon cycle. Despite this far-reaching importance, empirical estimates of long-term trends in phytoplankton abundance remain limited.” - Edward A. G. Schuur et al (2008) – Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle – BioScience 58:701-714 doi:10.1641/B580807 – 01/09/2008 – Department of Botany at the University of Florida – 19 authors – Peer-reviewed
“We show that accounting for C stored deep in the permafrost more than doubles previous high-latitude inventory estimates, with this new estimate equivalent to twice the atmospheric C pool. The thawing of permafrost with warming occurs both gradually and catastrophically, exposing organic C to microbial decomposition. Other aspects of ecosystem dynamics can be altered by climate change along with thawing permafrost, such as growing season length, plant growth rates and species composition, and ecosystem energy exchange. However, these processes do not appear to be able to compensate for C release from thawing permafrost, making it likely that the net effect of widespread permafrost thawing will be a positive feedback to a warming climate.” - C. Tarnocai et al (2009) – Soil organic carbon pools in the northern circumpolar permafrost region – Global Biogeochemical Cycles 3:GB2023 doi:10.1029/2008GB003327 – 27/06/2009 – Research Branch, Agriculture and Agri-Food Canada – 6 authors – Peer-reviewed
“The Northern Circumpolar Soil Carbon Database was developed in order to determine carbon pools in soils of the northern circumpolar permafrost region. The area of all soils in the northern permafrost region is approximately 18,782 × 103 km2, or approximately 16% of the global soil area. In the northern permafrost region, organic soils (peatlands) and cryoturbated permafrost-affected mineral soils have the highest mean soil organic carbon contents (32.2–69.6 kg m−2). Here we report a new estimate of the carbon pools in soils of the northern permafrost region, including deeper layers and pools not accounted for in previous analyses. Carbon pools were estimated to be 191.29 Pg for the 0–30 cm depth, 495.80 Pg for the 0–100 cm depth, and 1024.00 Pg for the 0–300 cm depth. Our estimate for the first meter of soil alone is about double that reported for this region in previous analyses. Carbon pools in layers deeper than 300 cm were estimated to be 407 Pg in yedoma deposits and 241 Pg in deltaic deposits. In total, the northern permafrost region contains approximately 1672 Pg of organic carbon, of which approximately 1466 Pg, or 88%, occurs in perennially frozen soils and deposits. This 1672 Pg of organic carbon would account for approximately 50% of the estimated global belowground organic carbon pool.» - Timothy M. Lenton et al (2008) – Tipping elements in the Earth’s climate system – Proceedings of the National Academy of Sciences PNAS 105:1786-1793 doi:10.1073/pnas.0705414105 – 12/02/2008 – School of Environmental Sciences, University of East Anglia, and Tyndall Centre for Climate Change Research – 7 authors – Peer-reviewed
“We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and we assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then we explain how, in principle, early warning systems could be established to detect the proximity of some tipping points.” - Joseph Romm – The IPCC lowballs likely impacts with its instantly out-of-date reports and is clearly clueless on messaging – should it be booted or just rebooted? And should IPCC chief Pachauri stay or go? – Climate Progress – 18/02/2010 – http://climateprogress.org/2010/02/18/ipcc-lowballs-impacts-pachauri-disband/
“Most of the climate models had not yet incorporated many if any of the amplifying carbon cycle feedbacks … Indeed, not a single one of the climate models they rely on incorporates the single most dangerous feedback, the defrosting of the permafrost.” - Joseph Romm – Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius” – Climate Progress – 26/10/2008 – http://climateprogress.org/2008/10/26/study-water-vapor-feedback-is-strong-and-positive-so-we-face-warming-of-several-degrees-celsius/
“The major climate models are missing key amplifying feedbacks, some of which were discussed in “Are Scientists Underestimating Climate Change, Part II.” These feedbacks include: The defrosting of the permafrost; The drying of the Northern peatlands (bogs, moors, and mires); The destruction of the tropical wetlands; Decelerating growth in tropical forest trees — thanks to accelerating carbon dioxide; Wildfires and Climate-Driven forest destruction by pests; The desertification-global warming feedback; The saturation of the ocean carbon sink.” - Ryouta O’ishiet al (2009) – Vegetation dynamics and plant CO2 responses as positive feedbacks in a greenhouse world – Geophysical Research Letters 36 L11706 doi:10.1029/2009GL038217 – 06/06/2009 – 4 authors – Peer-reviewed
“The biospheric response to CO2 and climate change becomes dominated by positive feedbacks that overwhelm the effect of CO2 fertilization on terrestrial carbon stocks … This feedback amplifies global warming by 13%. About half of it is due to climatically induced expansion of boreal forest into tundra, reinforced by reductions in snow and sea ice cover. The other half represents a global climatic effect of increased vegetative cover (an indirect consequence of plant physiological responses to CO2) in the semi-arid subtropics.” - Abigail L. Swanna et al (2010) – Changes in Arctic vegetation amplify high-latitude warming through the greenhouse effect – Proceedings of the National Academy PNAS Early Edition doi:10.1073/pnas.0913846107 – 01/12/2010 – Department of Earth & Planetary Science, University of California – 5 authors – Peer-reviewed
“Land surface albedo change is considered to be the dominant mechanism by which trees directly modify climate at high-latitudes, but our findings suggest an additional mechanism through transpiration of water vapor and feedbacks from the ocean and sea-ice … The long-wave effects from changes in atmospheric moisture are not generally considered in studies of high-latitude vegetation change, but we find the radiative forcing from water vapor to be the same magnitude as the direct shortwave forcing from albedo, indicating that the energy budget of the entire column should be considered and not just the balance of surface fluxes.” - Chris Mooney (2007) – Storm World. Hurricanes, Politics and the Battle Over Global Warming – Hartcourt Books
«The ‘most important and obvious’ positive feedback identified in the Charney report involved atmospheric water vapor. Due to a physical law known as the Clausius-Clapeyron equation, the amount of moisture that can be carried by the air increases along a steeply sloping curve as temperature rises.» - Richard S. Lindzen, Ming-Dah Chou and Arthur Y. Hou (2001) – Does the earth have an adaptive infrared iris? – Bulletin of the American Meteorological Society BAMS 82:417-432 – ‘Peer-reviewed’
“This new mechanism would, in effect, constitute an adaptive infrared iris that opens and closes in order to control the Outgoing Longwave Radiation in response to changes in surface temperature in a manner similar to the way in which an eye’s iris opens and closes in response to changing light levels.” - Dennis L. Hartmann and Marc L. Michelsen (2001) – No Evidence for Iris – Bulletin of the American Meteorological Society BAMS February 2002:249-254 – Peer-reviewed
“It is unreasonable to interpret these changes as evidence that deep tropical convective anvils contract in response to SST increases. Moreover, the nature of the cloudweighted SST statistic is such that any variation in cloud fraction over the coldest water must produce a negative correlation with cloud fraction, a fact that has no useful interpretation in climate sensitivity analysis. Therefore, the observational analysis in LCH lends no support to the hypothesis that increased SST decreases the area covered by tropical anvil cloud.” - Kevin E. Trenberth – Testimony on ‘The 2001 Assessment of Climate Change’ before The US Senate Committee on Environment and Public Works – National Center for Atmospheric Research – 02/05/2001 – ‘Peer-reviewed’
“Recent possibilities that might nullify global warming (Lindzen 2001) were considered but not accepted because they run counter to the prevailing evidence, and the IPCC (Stocker et al. 2001) concluded that “the balance of evidence favours a positive clear sky water vapour feedback of the magnitude comparable to that found in the simulations … The best assessment of global warming is that the human climate signal emerged from the noise of background variability in the late 1970s.” - Takmeng Wong, Bruce A. Wielicki, And Robert B. Lee Iii, G. Louis Smith, Kathryn A. Bush, Joshua K. Willis (2006) – Re-examination of the Observed Decadal Variability of the Earth Radiation Budget Using Altitude-Corrected ERBE/ERBS Nonscanner WFOV Data – Journal of Climate 19:4028:4040 – 15/08/2006 – NASA Langley Research Center; National Institute of Aerospace; Science Applications International Jet Propulsion Laboratory, California Institute of Technology Corporation – ‘Peer-reviewed’
“The new results do not support the recent Iris hypothesis (Lindzen et al. 2001; Lin et al. 2004). As tropical and global SST warms in the late 1990s during the 1997–98 El Niño, the Iris negative feedback predicts net flux to decrease (ocean cooling) as opposed to the increase (ocean heating) seen.” - Gavin Schmidt (2010) – Taking the Measure of the Greenhouse Effect – NASA Science Briefs – 01/10/2010 – http://www.giss.nasa.gov/research/briefs/schmidt_05/ – ‘Peer-reviewed’
«We find that water vapor is the dominant substance — responsible for about 50% of the absorption, with clouds responsible for about 25% — and CO2 responsible for 20% of the effect. The remainder is made up with the other minor greenhouse gases, ozone and methane for instance, and a small amount from particles in the air (dust and other «aerosols»).» - Walter Williams – Las delirantes predicciones de los ecologistas – Grupo de Estudios Estratégicos – 14/05/2008 – http://www.gees.org/articulos/las_delirantes_predicciones_de_los_ecologistas_5484
“He aquí algunos datos: más del 95 por ciento del efecto invernadero es resultado del vapor de agua en la atmósfera de la Tierra. Sin el efecto invernadero, la temperatura media de la Tierra sería de cero grados Fahrenheit. La mayor parte del cambio climático es resultado de las excentricidades orbitales de la Tierra y las variaciones en las emisiones del sol.” - Andrew E. Dessler, Z. Zhang, and P. Yang (2008) – Water-vapor climate feedback inferred from climate fluctuations, 2003-2008 – Geophysical Research Letters 35 L20704 doi:10.1029/2008GL035333 – 23/10/2008 – Department of Atmospheric Sciences, Texas A&M University – ‘Peer-reviewed’
“Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations … The water-vapor feedback implied by these observations is strongly positive … means that projected business-as-usual greenhouse-gas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius. The only way that will not happen is if a strong, negative, and currently unknown feedback is discovered somewhere in our climate system.” - Andrew E. Dessler and Steven C. Sherwood (2009) – A Matter of Humidity – Science 323:1020-1021 doi:10.1126/science.1171264 – 20/02/2009 – Texas A&M University; Climate Change Research Centre, University of New South Wales, Sydney – ‘Peer-reviewed’
“How strong a part does water vapor play in global warming? … the water vapor feedback is virtually certain to be strongly positive, with most evidence supporting a magnitude of 1.5 to 2.0 W/m2/K, sufficient to roughly double the warming that would otherwise occur.” - Andrew A. Lacis et al (2010) – Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature – Science 330:356-359 doi:10.1126/science.1190653 – 14/10/2010 – NASA Goddard Institute for Space Studies- 4 authors – ‘Peer-reviewed’
«A clear demonstration is needed to show that water vapor and clouds do indeed behave as fast feedback processes and that their atmospheric distributions are regulated by the sustained radiative forcing due to the non-condensing GHGs. To this end, we performed a simple climate experiment with the GISS 2° × 2.5° AR5 version of ModelE, using the Q-flux ocean with a mixedlayer depth of 250 m, zeroing out all the non-condensing GHGs and aerosols.» - Ben D. Santer et al (2008) – Incorporating model quality information in climate change detection and attribution Studies – Proceedings of the National Academy of Sciences PNAS Early Edition doi:10.1073/pnas.0901736106 – 14/08/2008 – Program for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National Laboratory – Edited by Michael E. Mann, Pennsylvania State University, University Park, PA- 15 authors – ‘Peer-reviewed’
“We find that estimates of an anthropogenic water vapor fingerprint are insensitive to current model uncertainties, and are governed by basic physical processes that are well-represented in climate models. Because the fingerprint is both robust to current model uncertainties and dissimilar to the dominant noise patterns, our ability to identify an anthropogenic influence on observed multidecadal changes in water vapor is not affected by ‘‘screening’’ based on model quality.” - Richard A. Kerr (2008) – Another Side to the Climate-Cloud Conundrum Finally Revealed – Science 319:889 doi:10.1126/science.319.5865.889a – 15/02/2008 – Director de Science – ‘Peer-reviewed’
“The clouds in their models are crude at best, and in the real world, researchers struggle to understand how clouds are responding to–and perhaps magnifying–greenhouse warming. As a result, cloud behavior is the biggest single source of uncertainty in climate prediction. But two new studies now show that much of the worry about clouds’ role in the warming has been misdirected. Clouds’ response to global temperature changes may be much quicker and more direct–and thus easier to study–than experts have thought … The nature of the feedback remains mysterious, but if it’s positive, it would decrease global cloud cover. With fewer clouds reflecting solar energy back into space, more energy would reach Earth, amplifying the initial warming.” - Kevin E. Trenberth and John T. Fasullo (2009) – Global warming due to increasing absorbed solar radiation – Geophysical Research Letters 36 L07706 doi:10.1029/2009GL037527 – 14/04/2009 – National Center for Atmospheric Research – ‘Peer-reviewed’
“There is an increase in net radiation absorbed, but not in ways commonly assumed. While there is a large increase in the greenhouse effect from increasing greenhouse gases and water vapor (as a feedback), this is offset to a large degree by a decreasing greenhouse effect from reducing cloud cover and increasing radiative emissions from higher temperatures. Instead the main warming from an energy budget standpoint comes from increases in absorbed solar radiation that stem directly from the decreasing cloud amounts.” - Amy C. Clement et al (2009) – Observational and Model Evidence for Positive Low-Level Cloud Feedback – Science 325:460-464 doi:10.1126/science.1171255 – 24/07/2009 – Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Division of Meteorology and Physical Oceanography – 3 authors – ‘Peer-reviewed’
“This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales … The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.” - Amy C. Clement et al (2009) – Observational and Model Evidence for Positive Low-Level Cloud Feedback – Science 325:460-464 doi:10.1126/science.1171255 – 24/07/2009 – Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Division of Meteorology and Physical Oceanography – ‘Peer-reviewed’
“The question of whether low-level clouds act as a positive or negative feedback to climate change has been an issue for decades. The analysis presented here provides observational evidence that this feedback is positive in the NE Pacific on decadal time scales. The only model in the CMIP3 archive that properly simulates clouds in the NE Pacific and exhibits 2 × CO2 circulation changes that are consistent with multimodel mean produces a reduction in cloud throughout much of the Pacific in response to greenhouse gas forcing (i.e., a positive feedback).” - Richard A. Kerr (2009) – Clouds Appear to Be Big, Bad Player in Global Warming – Science 325:376 doi:10.1126/science.325_376 – 24/07/2009 – Director de Science – ‘Peer-reviewed’
«When the results were in, only two models showed low clouds producing a positive feedback as observed. One of them stood out from the pack. The HadGEM1 model from the U.K. Met Office’s Hadley Center in Exeter produced patterns of warming and circulation changes during greenhouse warming that resembled those of all 18 models averaged together—the best guide available. The group also concluded that HadGEM1’s simulation of meteorological processes in the lowermost kilometer or two of the atmosphere—where the key low-lying clouds reside—is particularly realistic. « - Amy C. Clement et al (2009) – Observational and Model Evidence for Positive Low-Level Cloud Feedback – Science 325:460-464 doi:10.1126/science.1171255 – 27/07/2009 – Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, Division of Meteorology and Physical Oceanography – 3 authors – ‘Peer-reviewed’
“Evaluating cloud feedback with one model is, however, far from ideal. This presents a clear challenge to develop a larger number of climate models that can pass these and other tests so that we may have greater confidence in the sign of the low-cloud feedback under future changes in greenhouse gas concentrations.” - Gisela Speidel – Study could mean greater anticipated global warming – University of Hawaii – 22/09/2010 – http://www.eurekalert.org/pub_releases/2010-11/uoha-scm112210.php
«The regional model, developed at the IPRC, successfully simulates key features of the region’s present-day cloud fields, including the observed response of clouds to El Nino. Having evaluated the model’s simulation of present-day conditions, the researchers examined the response of simulated clouds in a warmer climate such as it might be in 100 years from now. The tendency for clouds to thin and cloud cover to reduce was more pronounced in this model than in any of the current global models.» - Axel Lauer et al (2010) – The Impact of Global Warming on Marine Boundary Layer Clouds over the Eastern Pacific: A Regional Model Study – Journal of Climate 23:5844-5863 doi:10.1175/2010JCLI3666.1 – November 2010 – International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii – ‘Peer-reviewed’
“If our model results prove to be representative of the real global climate, then climate is actually more sensitive to perturbations by greenhouse gases than current global models predict, and even the highest warming predictions would underestimate the real change we could see.» - L.S. Peck et al (2009) – Negative feedback in the cold: ice retreat produces new carbon sinks in Antarctica – Global Change Biology doi:10.1111/j.1365-2486.2009.02071.x – Accepted 29/08/2009 – British Antarctic Survey, Natural Environment Research Council – 5 authors – ‘Peer-reviewed’
“We estimate that these new areas of open water have allowed new phytoplankton blooms containing a total standing stock of ~5.0×105 tonnes of carbon to be produced. New marine zooplankton and seabed communities have also been produced, which we estimate contain ~ 4.1×105 tonnes of carbon. This previously unquantified carbon sink acts as a negative feedback to climate change. As ice loss increases in polar regions this feedback will become stronger, and eventually, over thousands to hundreds of housands of years, over 50Mtonnes of new carbon could be fixed annually in new coastal phytoplankton blooms and over 10 Mtonnes yr-1 locked in biological standing stock around Antarctica.” - Daniel G. Boyce, Marlon R. Lewis and Boris Worm (2010) – Global phytoplankton decline over the past century – Nature 466:591–596 doi:10.1038/nature09268 – 29/07/2010 – Biology Department, Dalhousie University – Peer-reviewed
“We observe declines in eight out of ten ocean regions, and estimate a global rate of decline of ~1% of the global median per year. Our analyses further reveal interannual to decadal phytoplankton fluctuations superimposed on long-term trends. These fluctuations are strongly correlated with basin-scale climate indices, whereas long-term declining trends are related to increasing sea surface temperatures. We conclude that global phytoplankton concentration has declined over the past century; this decline will need to be considered in future studies of marine ecosystems, geochemical cycling, ocean circulation and fisheries.” - Vladimir E. Romanovsky et al (2001) – Permafrost Temperature Dynamics Along the East Siberian Transect and an Alaskan Transect (Extended Abstract) – Tôhoku Geophysical Journal 36:224-229 – Received 08/11/2000 – Geophysical Institute , University of Alaska Fairbanks – 5 authors – ‘Peer-reviewed’
“The results show that in general interannual and decadal variability in the air temperatures significantly increases «inertia» of permafrost to degradation. Cold «extreme events» refreeze the shallow taliks developed during the warm periods, and «recharge» permafrost with additional cold. For the scenario with a trend, after 2040 permafrost at the Fairbanks site shows continuous thawing. However, for the both Fairbanks and Yakutsk sites, the period from 2015 to 2025 (2020 to 2030 for Yakutsk) will see the beginning of permafrost instability and degradation . During these times, thermokarst processes may become very active affecting ecosystems and infrastructures in these regions … Disturbances related to forest fires significantly increase the probability of permafrost degradation in the near future. Our temperature measurements and calculations show that for most of the time after 1975, the mean annual ground surface temperatures at the Fairbanks sites were (and probably will be) above 0°C.” - David M. Lawrence and Andrew G. Slater (2005) – A projection of severe near-surface permafrost degradation during the 21st century – Geophysical Research Letters, 32, L24401, doi:10.1029/2005GL025080 – 17/12/2005 – Climate and Global Dynamics Division, National Center for Atmospheric Research – ‘Peer-reviewed’
“The current distribution and future projections of permafrost are examined in a fully coupled global climate model, the Community Climate System Model, version 3 (CCSM3) with explicit treatment of frozen soil processes. The spatial extent of simulated present-day permafrost in CCSM3 agrees well with observational estimates – an area, excluding ice sheets, of 10.5 million km2. By 2100, as little as 1.0 million km2 of near-surface permafrost remains. Freshwater discharge to the Arctic Ocean rises by 28% over the same period, largely due to increases in precipitation that outpace increases in evaporation, with about 15% of the rise directly attributable to melting ground ice. Such large changes in permafrost may provoke feedbacks such as activation of the soil carbon pool and a northward expansion of shrubs and forests.” - Edward A. G. Schuur et al (2008) – Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle – BioScience 58:701-714 doi:10.1641/B580807 – 01/09/2008 – Department of Botany at the University of Florida – 19 authors – ‘Peer-reviewed’
“Accurate prediction of the magnitude and effect of thawing permafrost on global climate remains difficult, however, for several reasons. The core conceptual issue is that the change from ice to liquid water represents a nonlinear threshold whose effects on ecosystem dynamics are difficult to capture with current modeling approaches. Terrestrial ecosystem model simulations that examine the effects of climate change and biogeochemical feedbacks to the climate system in northern high-latitude ecosystems are few, and do not represent most of the permafrost thawing dynamics or deep soil C stocks described in this review. At broader scales, global circulation models are just beginning to include simple permafrost dynamics.” - David M. Lawrence et al (2010) – Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss – Geophysical Research Letters 35, L11506, doi:10.1029/2008GL033985 – 07/03/2008 – Climate and Global Dynamics Division, National Center for Atmospheric Research – 5 authors – ‘Peer-reviewed’
“We find that western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends outside these periods. The accelerated warming signal extends up to 1500km inland and is apparent throughout most of the year, peaking in autumn. Idealized experiments using the Community Land Model, with improved permafrost dynamics, indicate that an accelerated warming period substantially increases ground heat accumulation – the earlier the event the greater the long-term impact. For warm permafrost, enhanced heat accumulation can lead to rapid degradation. For colder ground, heat accumulation preconditions permafrost for earlier and/or more rapid degradation under continued warming.” - P. Kuhry et al (2010) – Potential remobilization of belowground permafrost carbon under future global warming – Permafrost and Periglacial Processes 21:208–214 DOI:10.1002/ppp.684 – 08/06/2010 – Department of Physical Geography and Quaternary Geology, Stockholm University – 5 authors – ‘Peer-reviewed’
“Recent findings in Alaska and northern Sweden provide strong evidence that the deeper soil carbon in permafrost terrain is starting to be released, supporting previous reports from Siberia. The permafrost carbon pool is not yet fully integrated in climate and ecosystem models and an important objective should be to define typical pedons appropriate for model setups. The thawing permafrost carbon feedback needs to be included in model projections of future climate change.” - David Ljunggren – Arctic Tundra Hotter, Boosts Global Warming: Expert – Climate Change Psychology – 31/07/2009 – http://climatechangepsychology.blogspot.com/2009/08/greg-henry-arctic-tundra-around-world.html
“[Greg Henry]: We’re finding that the tundra is actually giving off a lot more nitrous oxide and methane than anyone had thought before,» Henry told reporters on a conference call from Resolute in the northern Canadian territory of Nunavut. «We’re really trying to get a handle on this because if (further tests show) that’s true, this actually changes the entire greenhouse gas budget for the North, and that has global implications,» he said.”” - D. Nicolsky and N. Shakhova (2010) – Modeling sub-sea permafrost in the East Siberian Arctic Shelf: the Dmitry Laptev Strait – Environment Research Letters 5 015006 doi:10.1088/1748-9326/5/1/015006 – 25/03/2010 – Geophysical Institute, University of Alaska Fairbanks; International Arctic Research Center, University of Alaska Fairbanks – http://iopscience.iop.org/1748-9326/5/1/015006/fulltext – ‘Peer-reviewed’
“The present state of sub-sea permafrost modeling does not agree with certain observational data on the permafrost state within the East Siberian Arctic Shelf. This suggests a need to consider other mechanisms of permafrost destabilization after the recent ocean transgression. We propose development of open taliks wherever thaw lakes and river paleo-valleys were submerged shelf-wide as a possible mechanism for the degradation of sub-sea permafrost. To test the hypothesis we performed numerical modeling of permafrost dynamics in the Dmitry Laptev Strait area. We achieved sufficient agreement with the observed distribution of thawed and frozen layers to suggest that the proposed mechanism of permafrost destabilization is plausible.” - J. Hollesen et al (2010) – Future active layer dynamics and carbon dioxide production from thawing permafrost layers in Northeast Greenland – Global Change Biology doi:10.1111/j.1365-2486.2010.02256.x – 22/04/2010 – Department of Geography and Geology, University of Copenhagen – 3 authors – ‘Peer-reviewed’
“The model predicts an increase of maximum active layer thickness from today 70 to 80–105 cm as a result of a 2–6 °C warming … Results show an increase from present values of <40 g C m−2 yr−1 to between 120 and 213 g C m−2 yr−1 depending on the magnitude of predicted warming. These rates are more than 50% of the present soil CO2 efflux measured at the soil surface. Future modelling accounting for snow, vegetation and internal «biological heat feedbacks are of interest in order to test the robustness of the above predictions and to describe the entire ecosystem response.” - Natalia Shakhova et al (2010) – Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf – Science 327:1246-1250 doi:10.1126/science.1182221 – 05/03/2010 – International Arctic Research Centre, University of Alaska, Fairbanks – 6 authors – ‘Peer-reviewed’
“Here, we show that more than 5000 at-sea observations of dissolved methane demonstrates that greater than 80% of [East Siberian Arctic Shelf] ESAS bottom waters and greater than 50% of surface waters are supersaturated with methane regarding to the atmosphere. The current atmospheric venting flux, which is composed of a diffusive component and a gradual ebullition component, is on par with previous estimates of methane venting from the entire World Ocean. Leakage of methane through shallow ESAS waters needs to be considered in interactions between the biogeosphere and a warming Arctic climate … To discern whether this extensive CH4 venting over the ESAS is a steadily ongoing phenomenon or signals the start of a more massive CH4 release period, there is an urgent need for expanded multifaceted investigations into these inaccessible but climate-sensitive shelf seas north of Siberia.” - K. M. Walter et al (2006) – Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming – Nature 443 71-75 doi:10.1038/nature05040 – 07/09/2006 – Institute of Arctic Biology, University of Alaska Fairbanks – 5 authors – ‘Peer-reviewed’
“We show that ebullition accounts for 95 per cent of methane emissions from these lakes, and that methane flux from thaw lakes in our study region may be five times higher than previously estimated.” - Philipp Schneider and Simon J. Hook (2010) – Space observations of inland water bodies show rapid surface warming since 1985 – Geophysical Research Letters 37, L22405, doi:10.1029/2010GL045059 – 24/11/2010 – Jet Propulsion Laboratory, California Institute of Technology
“Surface temperatures were extracted from night-time thermal infrared imagery of 167 large inland water bodies distributed worldwide beginning in 1985 for the months July through September and January through March. Results indicate that the mean night-time surface water temperature has been rapidly warming for the period 1985–2009 with an average rate of 0.045 ± 0.011°C yr−1 and rates as high as 0.10 ± 0.01°C yr−1. Worldwide the data show far greater warming in the mid- and high latitudes of the northern hemisphere than in low latitudes and the southern hemisphere. The analysis … indicates that water bodies in some regions warm faster than regional air temperature.” - Ben Bond-Lamberty and Allison Thomson (2010) – Temperature-associated increases in the global soil respiration record – Nature 464:579-582 doi:10.1038/nature08930 – 25/03/2010 – Pacific Northwest National Laboratory, Joint Global Change Research Institute, University of Maryland – ‘Peer-reviewed’
”We find that the air temperature anomaly (the deviation from the 1961–1990 mean) is significantly and positively correlated with changes in RS [soil respiration]. We estimate that the global RS in 2008 (that is, the flux integrated over the Earth’s land surface over 2008) was 98 ± 12 Pg C and that it increased by 0.1 Pg C yr-1 between 1989 and 2008, implying a global RS response to air temperature (Q10) of 1.5. An increasing global RS value does not necessarily constitute a positive feedback to the atmosphere, as it could be driven by higher carbon inputs to soil rather than by mobilization of stored older carbon. The available data are, however, consistent with an acceleration of the terrestrial carbon cycle in response to global climate change.» - Steven D. Allison et al (2010) – Soil-carbon response to warming dependent on microbial physiology – Nature Geoscience doi:10.1038/NGEO846 – 40293 – Department of Ecology and Evolutionary Biology, Department of Earth System Science, University of California – http://www.nature.com/ngeo/journal/v3/n5/pdf/ngeo846.pdf – 3 authors – ‘Peer-reviewed’
“We find that declines in microbial biomass and degradative enzymes can explain the observed attenuation of soil-carbon emissions in response to warming. Specifically, reduced carbon-use efficiency limits the biomass of microbial decomposers and mitigates the loss of soil carbon. However, microbial adaptation or a change in microbial communities could lead to an upward adjustment of the efficiency of carbon use, counteracting the decline in microbial biomass and accelerating soil-carbon loss. We conclude that the soil-carbon response to climate warming depends on the efficiency of soil microbes in using carbon.” - M.D. Mahecha, M. Reichstein, N. Carvalhais et al (2010) – Global Convergence in the Temperature Sensitivity of Respiration at Ecosystem Level – Science 329:838-840 doi:10.1126/science.1189587 – 24/08/2010 – Max Planck Institute for Biogeochemistry – 14 authors – ‘Peer-reviewed’
“Contrary to previous findings, our results suggest that Q10 [the sensitivity of terrestrial ecosystem respiration to air temperature] is independent of mean annual temperature, does not differ among biomes, and is confined to values around 1.4 ± 0.1 … The results may partly explain a less pronounced climate–carbon cycle feedback than suggested by current carbon cycle climate models … Our findings offer substantial evidence for the existence of universal intrinsic temperature sensitivities of terrestrial ecosystem respiration … Moreover, our results may partly explain recent findings indicating a less pronounced climate– carbon cycle sensitivity (ref) than assumed by current climate–carbon cycle model parameterizations.” - Pete Smith and Changming Fang – A warm response by soils – Nature 464:499-500 doi:10.1038/news.2010.147 – 25/03/2010 – Institute of Biological and Environmental Sciences, School of Biological Sciences, University of Aberdeen – http://www.nature.com/nature/journal/v464/n7288/full/464499a.html – ‘Peer-reviewed’
The outcomes of their meta-analysis should further drive efforts to develop methods to disaggregate the underlying processes contributing to RS. Without understanding these processes, it will not be possible to accurately predict the net response of soil carbon stores to climate change — and that is a central question for determining the biospheric feedbacks between the carbon cycle and climate.” - T. Eglin et al (2010) – Historical and future perspectives of global soil carbon response to climate and land-use changes – Tellus B doi:10.1111/j.1600-0889.2010.00499.x – 20/07/2010 – 11 authors – ‘Peer-reviewed’
“In this paper, we attempt to analyse the respective influences of land-use and climate changes on the global and regional balances of soil organic carbon (SOC) stocks … In the future, according to terrestrial biosphere and climate models projections, both climate and land cover changes might cause a net SOC loss, particularly in tropical regions. The timing, magnitude, and regional distribution of future SOC changes are all highly uncertain. Reducing this uncertainty requires improving future anthropogenic CO2 emissions and land-use scenarios and better understanding of biogeochemical processes that control SOC turnover, for both managed and un-managed ecosystems.” - C. Beer, M. Reichstein, E. Tomelleri et al (2010) – Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and Covariation with Climate – Science 329:834-838 doi:10.1126/science.1184984 – 24/08/2010 – Biogeochemical Model-Data Integration Group, Max Planck Institute for Biogeochemistry – 24 authors – ‘Peer-reviewed’
«Our findings imply a high susceptibility of these ecosystems’ productivity to projected changes of precipitation over the 21st century (ref), but a robustness of tropical and boreal forests. Results of current process models show a large range and a tendency to overestimate precipitation-associated GPP [Global Primary Productivity) (fig). Most likely, the association of GPP and climate in process-oriented models can be improved by including negative feedback mechanisms (e.g., adaptation) that might stabilize the systems. Our high spatial resolution GPP estimates, their uncertainty, and their relationship to climate drivers should be useful for evaluating and thus improving coupled climate–carbon cycle process models.» - David C. Frank et al (2010) – Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate – Nature 463:527-530 doi:10.1038/nature08769 – 28/01/2010 – Swiss Federal Research Institute WSL – 7 authors – ‘Peer-reviewed’
“Here we quantify the median γ as 7.7 ppmv CO2 per °C warming, with a likely range of 1.7–21.4 ppmv CO2 per °C. Sensitivity experiments exclude significant influence of pre-industrial land-use change on these estimates. Our results, based on the coupling of a probabilistic approach with an ensemble of proxy-based temperature reconstructions and pre-industrial CO2 data from three ice cores, provide robust constraints for γ on the policy-relevant multi-decadal to centennial timescales … Our results are incompatibly lower (P < 0.05) than recent pre-industrial empirical estimates of ~40 p.p.m.v. CO2 per °C (refs 6, 7), and correspondingly suggest ~80% less potential amplification of ongoing global warming.” - Andrew E. Dessler (2010) – A Determination of the Cloud Feedback from Climate Variations over the Past Decade – Science 330:1523-1527 doi:10.1126/science.1192546 – 10/12/2010 – Department of Atmospheric Sciences, Texas A&M University
“For the problem of long-term climate change, what we really want to determine is the cloud feedback in response to long-termclimate change. Unfortunately, it may be decades before a direct measurement is possible. In the meantime, observing shorter-term climate variations and comparing those observations to climate models may be the best we can do. This is what I have done in this paper. My analysis suggests that the short-term cloud feedback is likely positive and that climate models as a group are doing a reasonable job of simulating this feedback, providing some indication that models successfully simulate the response of clouds to climate variations.However, owing to the apparent time-scale dependence of the cloud feedback and the uncertainty in the observed short-term cloud feedback, we cannot use this analysis to reduce the present range of equilibrium climate sensitivity of 2.0 to 4.5 K.”
25/02/2009
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