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Climate change

About: Climate change is a research topic. Over the lifetime, 99222 publications have been published within this topic receiving 3572006 citations.


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Journal ArticleDOI
TL;DR: In this paper, the authors discuss the most promising approaches to early warning of tipping points in a climate system, where an external forcing causes a qualitative change in a system, such as the Greenland ice sheet tipping point.
Abstract: A tipping point occurs when an external forcing causes a qualitative change in a system. Human-induced climate change could push several large elements of the climate system, such as the Greenland ice sheet, past a tipping point. Given the severity of the potential impacts, early warning of these changes would be advantageous. This Review discusses the most promising approaches to early warning of tipping points.

652 citations

Journal ArticleDOI
TL;DR: This paper presented an updated version of MAGICC, the simple carbon cycle-climate model used in past IPCC Assessment Reports with enhanced representation of time-varying climate sensitivities, carbon cycle feedbacks, aerosol forcings and ocean heat uptake characteristics.
Abstract: Current scientific knowledge on the future response of the climate system to human-induced perturbations is comprehensively captured by various model intercomparison efforts In the preparation of the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), intercomparisons were organized for atmosphere-ocean general circulation models (AOGCMs) and carbon cycle models, named "CMIP3" and "C 4 MIP", respectively Despite their tremendous value for the scientific community and policy makers alike, there are some difficulties in interpreting the results For example, radiative forcings were not standardized across the various AOGCM integrations and carbon cycle runs, and, in some models, key forcings were omitted Furthermore, the AOGCM analysis of plausible emissions pathways was restricted to only three SRES scenarios This study attempts to address these issues We present an updated version of MAGICC, the simple carbon cycle-climate model used in past IPCC Assessment Reports with enhanced representation of time-varying climate sensitivities, carbon cycle feedbacks, aerosol forcings and ocean heat uptake characteristics This new version, MAGICC6, is successfully calibrated against the higher complexity AOGCMs and carbon cycle models Parameterizations of MAGICC6 are provided The mean of the emulations presented here using MAGICC6 deviates from the mean AOGCM responses by only 22% on average for the SRES scenarios This enhanced emulation skill in comparison to previous calibrations is primarily due to: making a "like-with-like comparison" using AOGCM-specific subsets of forcings; employing a new calibration procedure; as well as the fact that the updated simple climate model can now successfully emulate some of the climate-state dependent effective climate sensitivities of AOGCMs The diagnosed effective climate sensitivity at the time of CO 2 doubling for the AOGCMs is on average 288 °C, about 033 °C cooler than the mean of the reported slab ocean climate sensitivities In the companion paper (Part 2) of this study, we examine the combined climate system and carbon cycle emulations for the complete range of IPCC SRES emissions scenarios and the new RCP pathways

651 citations

Journal ArticleDOI
TL;DR: In this article, a variety of observed data and model results are presented to describe the climate shift, and to understand some of the links within the coupled climate system that produced it.
Abstract: An abrupt change in the large-scale boreal winter circulation pattern over the North Pacific was observed during the mid-1970s. Most notably, this change was marked by a southward shift and intensification of the Aleutian Low and prevailing westerlies over the mid-latitude central and eastern Pacific. Associated changes in diverse North Pacific climatological, hydrological, and biological variables have been noted by numerous researchers. Intriguingly, the timing of these changes in the extra-tropical circulation was coincident with a shift in the background state of the coupled ocean-atmosphere system over the tropical Pacific. These changes include increases in SST over broad regions of the central and eastern tropical Pacific and an eastward displacement of the region of persistent convection in the western Pacific. This paper presents a variety of observed data and model results to describe the climate shift, and to understand some of the links within the coupled climate system that produced it. Five main findings are emphasized: (1) evidence of abrupt, simultaneous, and apparently related changes can be found in many fields and in many model results; the climate shift is not an artifact, (2) over the tropical Pacific the climate change represents a shift in the state of the coupled ocean-atmosphere system, some aspects of which resemble features associated with El Nino episodes. However, the shift in state is not well characterized as due to a change in the frequency of intensity of El Ni~no episodes; it is better described as a change in background mean state, (3) when forced with observed SSTs, both a very simple atmospheric model and a full general circulation model (GCM) qualitatively simulate aspects of the decadal-scale shift over the tropical Pacific, (4) when forced with observed surface wind stress, two ocean models of the tropical Pacific, in which surface heat fluxes are parameterized as Newtonian damping, reproduce some aspects of the near-equatorial decadal SST signal. However, the models do not reproduce the large changes in SST observed at higher latitudes of the tropical Pacific, suggesting that altered surface heat fluxes dominated in producing these changes, and (5) an important new finding of this study is the success of a GCM in reproducing important aspects of the observed mid-1970s shift in winter northern hemisphere circulation. Comparative analyses of the observed and GCM simulated circulation suggest the altered patterns of tropical Pacific SST and convection were important in forcing the changes in the mid-latitude circulation, a finding corroborated by recent GCM experiments.

651 citations

Journal ArticleDOI
TL;DR: In this article, a review of recent research on the drivers, feedbacks, and impacts of global desertification is presented, motivated by the increasing need to improve global food production and to sustainably manage ecosystems in the context of climate change.

651 citations

Journal ArticleDOI
TL;DR: The atmospheric chemistry governing tropospheric O( 3) mass balance, the effects of O(3) on stomatal conductance and net primary productivity, and implications for agriculture, carbon sequestration, and climate change are reviewed.
Abstract: Tropospheric ozone (O3) is a global air pollutant that causes billions of dollars in lost plant productivity annually. It is an important anthropogenic greenhouse gas, and as a secondary air pollutant, it is present at high concentrations in rural areas far from industrial sources. It also reduces plant productivity by entering leaves through the stomata, generating other reactive oxygen species and causing oxidative stress, which in turn decreases photosynthesis, plant growth, and biomass accumulation. The deposition of O3 into vegetation through stomata is an important sink for tropospheric O3, but this sink is modified by other aspects of environmental change, including rising atmospheric carbon dioxide concentrations, rising temperature, altered precipitation, and nitrogen availability. We review the atmospheric chemistry governing tropospheric O3 mass balance, the effects of O3 on stomatal conductance and net primary productivity, and implications for agriculture, carbon sequestration, and climate ch...

649 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20253
20247
202312,805
202223,277
20217,120
20206,646