Showing papers on "Runaway climate change published in 2003"

Water vapor feedback and global warming

Abstract: ■ Abstract Water vapor is the dominant greenhouse gas, the most important gaseous source of infrared opacity in the atmosphere. As the concentrations of other greenhouse gases, particularly carbon dioxide, increase because of human activity, it is centrally important to predict how the water vapor distribution will be affected. To the extent that water vapor concentrations increase in a warmer world, the climatic effects of the other greenhouse gases will be amplified. Models of the Earth’s climate indicate that this is an important positive feedback that increases the sensitivity of surface temperatures to carbon dioxide by nearly a factor of two when considered in isolation from other feedbacks, and possibly by as much as a factor of three or more when interactions with other feedbacks are considered. Critics of this consensus have attempted to provide reasons why modeling results are overestimating the strength of this feedback. Our uncertainty concerning climate sensitivity is disturbing. The range most often quoted for the equilibrium global mean surface temperature response to a doubling of CO2 concentrations in the atmosphere is 1.5C to 4.5C. If the Earth lies near the upper bound of this sensitivity range, climate changes in the twenty-first century will be profound. The range in sensitivity is primarily due to differing assumptions about how the Earth’s cloud distribution is maintained; all the models on which these estimates are based possess strong water vapor feedback. If this feedback is, in fact, substantially weaker than predicted in current models, sensitivities in the upper half of this range would be much less likely, a conclusion that would clearly have important policy implications. In this review, we describe the background behind the prevailing view on water vapor feedback and some of the arguments raised by its critics, and attempt to explain why these arguments have not modified the consensus within the climate research community.

How positive is the feedback between climate change and the carbon cycle

Abstract: Future climate change induced by atmospheric emissions of greenhouse gases is believed to have a large impact on the global carbon cycle. Several offline studies focusing either on the marine or on the terrestrial carbon cycle highlighted such potential effects. Two recent online studies, using ocean—atmosphere general circulation models coupled to land and ocean carbon cycle models, investigated in a consistent way the feedback between the climate change and the carbon cycle. These two studies used observed anthropogenic CO2 emissions for the 1860–1995 period and IPCC scenarios for the 1995–2100 period to force the climate – carbon cycle models. The study from the Hadley Centre group showed a very large positive feedback, atmospheric CO2 reaching 980 ppmv by 2100 if future climate impacts on the carbon cycle, but only about 700 ppmv if the carbon cycle is included but assumed to be insensitive to the climate change. The IPSL coupled climate – carbon cycle model simulated a much smaller positive feedback: climate impact on the carbon cycle leads by 2100 to an addition of less than 100 ppmv in the atmosphere. Here we perform a detailed feedback analysis to show that such differences are due to two key processes that are still poorly constrained in these coupled models: first Southern Ocean circulation, which primarily controls the geochemical uptake of CO2, and second vegetation and soil carbon response to global warming. Our analytical analysis reproduces remarkably the results obtained by the fully coupled models. Also it allows us to identify that, amongst the two processes mentioned above, the latter (the land response to global warming) is the one that essentially explains the differences between the IPSL and the Hadley results.

Climate Change: Causes, Effects, and Solutions

Abstract: Preface. Section I Climate Change -- Past, Present, and Future. 1. Earth and the Greenhouse Effect. Introduction. The Greenhouse Effect. Large--Scale Heat Redistribution. Greenhouse Gases. Warming Potentials. Summary. 2. Past Climate Change: Lessons From History. Introduction. Past Climate Change -- Six Historic Periods. Methods of Determining Past Climates and Ecosystems. Rapid Climate Change. Lessons of Past Climate Change. Summary. 3. Recent Climate Change: The Earth Responds. Introduction. Atmospheric Temperatures. Water Vapor and Precipitation. Clouds and Temperature Ranges. Ocean Circulation Patterns. Snow and Ice. Sea--Level Rise. Animal Populations. Vegetation. Attribution. Summary. 4. Future Climate Change: The Twenty--First Century and Beyond. Introduction. Global Climate Models. Feedback Loops and Uncertainties. Scenario--Based Climate Predictions. Regional Climates and Extreme Events. The Persistence of a Warmer Earth. Summary. Section II Ecological Effects on Climate Change. 5. Effects on Freshwater Systems. Introduction. Surface and Groundwater. Drought and Soil Moisture. Lake and Stream Biota. Human Infrastructure. Wetlands. The Cryosphere. Managing Water. Summary. 6. Effects on Terrestrial Ecosystems. Introduction. Geographic Shifts in Terrestrial Habitats. Vegetation--Climate Interactions. Effects of Disturbances. Loss of Biodiversity. Implications for Forest Management and Conservation Policy. Summary. 7. Climate Change and Agriculture. Introduction. Effects of Agriculture on Climate Change. Effects of Climate Change on Agriculture. US Agriculture. Global Agriculture. Summary. 8. Climate Change and the Marine Environment. Introduction. Sea--Level Rise. Ocean Currents and Circulation. Marine Biogeochemistry. Marine Ecosystems. Summary. Section III Human Dimensions of Climate Change. 9. Impacts on Human Settlement and Infrastructure. Introduction. Energy. Environmental Quality. Extreme Climatic Events. Human Settlements. Infrastructure. Summary. 10. Effects of Climate Change on Human Health. Introduction. Direct Effects of Heat Stress. Infectious Diseases. Air Quality. Interactions and Secondary Effects. Summary. 11. Mitigation: Reducing the Impacts. Introduction. Capture or Sequester Carbon Emissions. Reduce Global Warming or Its Effects by Geoengineering. Enhance Natural Carbon Sinks. Convert to Carbon--Free and Renewable Energy Technologies. Conserve Energy and Use It More Efficiently. Adapt to Climate Change. Taking Action. Summary. 12. Policy, Politics, and Economics of Climate Change. Introduction. International Cooperation -- From Montreal to Kyoto. Meeting Kyoto Targets. Post--Kyoto Developments. The Politics of Climate Change. Kyoto Without the United States. Benefits and Costs of Mitigating Climate Change. The Future -- What is Needed? Summary. Appendix A: Units. Appendix B: Abbreviations and Chemical Symbols. Appendix C: Websites on Climate Change Index.

Strong carbon cycle feedbacks in a climate model with interactive CO2 and sulphate aerosols

Abstract: [1] Carbon cycle feedbacks are a significant source of uncertainty in climate change projections, with the potential for strong positive feedbacks to accelerate the rate of anthropogenic global warming during the 21st century. A climate change experiment is presented which uses a General Circulation Model (GCM) in which both interactive carbon and sulphur cycles have been included for the first time, along with the natural climate forcings due to solar changes and volcanic aerosol. These extra climate forcing factors have a significant impact on both 20th century climate change and the contemporary land and ocean carbon sinks. The additional forcings act to delay by more than a decade the conversion of the land carbon sink to a source, but ultimately result in a more abrupt rate of CO2 increase with the land carbon source (which reaches 7 GtC yr−1 by 2100) exceeding the ocean carbon sink (which saturates at 5 GtC yr−1 by 2100) beyond about 2080.

The Impact of Climate Change and Feedback Processes on the Ocean Carbon Cycle

Abstract: We have been aware of the concept of global climate change since the advent of modern science in the 17th Century and the emergence of disciplines such as geology. However, it is only in the last century that a putative link, termed the ‘the Greenhouse Effect’ (Wood 1909), has been suggested between the atmospheric concentrations of particular gases and climate. The composition of the atmosphere has been studied routinely since the late fifties/early sixties with the establishment of monitoring sites for atmospheric CO2 (such as Mauna Loa) where the 40-year dataset clearly demonstrates the rise of atmospheric CO2 (Keeling et al. 1995). Similar anthropogenically-mediated increases in the atmos-pheric concentrations of other gases such as nitrous oxide and methane have also been recorded in the last 40 years (Bigg 1996; IPCC 2001). Such increases in the concentrations of these gases in the atmosphere alter the radiative forcing globally by decreasing the long-wave radiative flux leaving the trophosphere (Houghton et al. 1990) which is thought to lead to climatic effects. Alongside the global monitoring of atmospheric concentrations and distributions of greenhouse gases, there have been concerted efforts to use mathematical models to better understand the nature of the relationship between the observed changes in gas concentrations, subsequent alteration of radiative forcing and climate.

Palaeoclimatic insights into future climate challenges.

Abstract: Palaeoclimatic data document a sensitive climate system subject to large and perhaps difficult-to-predict abrupt changes. These data suggest that neither the sensitivity nor the variability of the climate are fully captured in some climate-change projections, such as the Intergovernmental Panel on Climate Change (IPCC) Summary for Policymakers. Because larger, faster and less-expected climate changes can cause more problems for economies and ecosystems, the palaeoclimatic data suggest the hypothesis that the future may be more challenging than anticipated in ongoing policy making. Large changes have occurred repeatedly with little net forcing. Increasing carbon dioxide concentration appears to have globalized deglacial warming, with climate sensitivity near the upper end of values from general circulation models (GCMs) used to project human-enhanced greenhouse warming; data from the warm Cretaceous period suggest a similarly high climate sensitivity to CO(2). Abrupt climate changes of the most recent glacial-interglacial cycle occurred during warm as well as cold times, linked especially to changing North Atlantic freshwater fluxes. GCMs typically project greenhouse-gas-induced North Atlantic freshening and circulation changes with notable but not extreme consequences; however, such models often underestimate the magnitude, speed or extent of past changes. Targeted research to assess model uncertainties would help to test these hypotheses.

Global Warming Could Have a Chilling Effect on the Military (Defense Horizons, Number 33, October 2003)

Abstract: : Most debates and studies addressing potential climate change have focused on the buildup of industrial greenhouse gases in the atmosphere and a gradual increase in global temperatures. But this "slow ramp" climate change scenario ignores recent and rapidly advancing evidence that Earth's climate repeatedly has become much colder, warmer, wetter, or drier-in time spans as short as three to 10 years. Earth's climate system appears to have sensitive thresholds, the crossing of which shifts the system into different modes of operation and triggers rapid, non-linear, and not necessarily global changes. This new paradigm of abrupt climate change does not appear to be on the radar screens of military planners, who treat climate change as a long term, low-level threat, with mostly sociological, not national security, implications. But intense and abrupt climate changes could escalate environmental issues into unanticipated security threats, and could compromise an unprepared military. The global ocean circulation system, often called the Ocean Conveyor, can change rapidly and shift the distribution patterns of heat and rainfall over large areas of the globe. The North Atlantic region is particularly vulnerable to abrupt regional coolings linked to ocean circulation changes. Global warming and ocean circulation changes also threaten the Arctic Ocean's sea ice cover. Beyond the abrupt climatic impacts, fundamental changes in ocean circulation also have immediate naval implications. Recent evidence suggests that the oceans already may be experiencing large-scale changes that could affect Earth's climate. Military planners should begin to consider potential abrupt climate change scenarios and their impacts on national defense.

Reducing UK residential carbon emissions by 60

Abstract: The Royal Commission on Environmental Pollution (RCEP) has identified that the UK needs to reduce its carbon dioxide emissions by 60% by 2050 if it is to play its part in preventing catastrophic climate change and to go down the road of sustainable development. This paper will summarise a UK government funded project, “The 40% house”, which aims to identify the main policy implications for the domestic sector if the challenging reduction in carbon dioxide emissions is to be achieved by 2050. The study considers both reduced demand and household-level new and renewable energy supply technologies. The assessment will be in terms of total energy consumption and power demand levels. The first task is to establish likely levels of consumption, as a result of trends in household numbers, equipment ownership, effects of climate change (on heating and cooling) and known policies. The potential for reductions will incorporate changed levels of building and demolition in the housing stock, decision trees on technology choices to avoid incompatibility, new Building Regulation standards, more efficient appliances and so forth. Consumer attitudes to, and choices from, lower carbon options will be investigated through focus groups, together with the impact of in-house energy supply (pv, micro-chp, etc). The main policy avenues will be identified partly through backcasting from the RCEP scenarios, as well as forecasting from the housing and domestic energy and carbon stock model. The project takes a broad, but thorough overview in order to identify the main issues for immediate action and more detailed analysis to enable faster progress towards the 40% house.

An examination of anthropogenic climate forcing in the 21st century: greenhouse gases and aerosols - direct and indirect

Abstract: The projection of future climate change - and its consequent impact on societies and individuals - depends not only on society's direct emissions of greenhouse gases and aerosols, but also on the Earth system's response to these changes insofar as they additionally alter the radiative forcing of climate. These feedbacks involve coupling across the physical climate and biogeochemical systems, and they are often also designated indirect effects. This report examines some of the more well identified and quantified indirect effects related to atmospheric composition, as well as those that, although identified, remain highly uncertain. Although the unpredictability of anthropogenic emissions of greenhouse agents over the 21st century dominates the uncertainty of future climate, these feedbacks are a major contribution; and the big question is how such global feedbacks could be detected and quantified. The detection of feedbacks, even from an integrated Earth observing system, is a major challenge. This report is based in large part on results from the IPCC/TAR and immediate follow-on studies, and this rapporteur thanks the many lead and contributing authors to the TAR.