New Peer-Reviewed Research Since IPCC WGI Deadline

Studies confirm and add detail to Working Group I Conclusions

Oct. 10, 2013 – (New York) On Sept. 27, the Intergovernmental Panel on Climate Change (IPCC) released the Summary for Policymakers (SPM) portion of its Working Group I report. The SPM pulled from more than 9,200 peer-reviewed studies as reviewed by more than 600 contributing authors. Noteworthy conclusions include the increased confidence that human activities have warmed the atmosphere and the quickened pace of change for climate impacts such as sea level rise, Arctic ice retreat and glacial melt.

This document offers a summary of the key findings, including putting the so-called “pause” of increased surface temperatures in context and offering scientific explanations for the slowdown. Despite the thousands of studies WGI authors reviewed, however, the IPCC has a self-imposed research deadline. For this portion of the Fifth Assessment (AR5), studies published later than mid-May were not included in the review.  

Research published in the last few months illustrates the incredible breadth of ongoing climate-related research and adds further detail to WGI conclusions. Some studies worth noting include:

— Balmaseda, Trenberth and Källén, "Distinctive climate signals in reanalysis of global ocean heat content," Geophysical Research Letters— This paper presents the most current data on the ocean's role in Earth's energy budget, lowering the uncertainty over the causes of the recent surface warming slowdown. Volcanic eruptions and El Niño cycles produce sharp cooling events punctuating a long-term ocean warming trend, while heating continues during the recent upper-ocean-warming hiatus, but the heat is absorbed in the deeper ocean.

— Diffenbaugh, Scherer and Trapp, “Robust increases in severe thunderstorm environments in response to greenhouse forcing,” Proceedings of the National Academy of Sciences of the United States of America — Using a new climate model experiment for tracking implications of global warming on extreme weather patterns in the United States, Diffenbaugh and his colleagues found climate change will likely produce more days with high convective available potential energy (CAPE) and sufficient wind shear. Together, these factors could create conditions that lead to severe thunderstorms and possible tornadoes.  

— Kosaka and Xie, "Recent global-warming hiatus tied to equatorial Pacific surface cooling,” Nature — Various mechanisms have been proposed to account for the hiatus in surface warming, but their relative importance has not been quantified. This paper reconciles climate simulations and observations by accounting for recent cooling in the eastern equatorial Pacific. The study presents a novel method of uncovering mechanisms for global temperature change by using the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model.

— Mearns et al., “Climate change projections of the North American Regional Climate Change Assessment Program (NARCCAP),” Climatic Change — Mearns and her colleagues found that climate change would increase summertime drying in parts of the central United States in the near future. The models also indicated “for the period 2041-2070 compared to 1971-2000, the Midwest and Northeast are likely to be more moist during the winter, while western and southern states are likely to face increasingly dry summers.”

— Parmesan et al., "Beyond climate change attribution in conservation and ecological research,” Ecology Letters — This paper argues that quantitative estimations of the relative contributions of different driving forces, including anthropogenic climate change (ACC), to observed biological changes are not productive for ecological studies.  Analyses of diverse species, regions and ecosystems have already given us "very high confidence" that ACC has impacted wild species. For well-studied species or systems, synthesis of experiments and models with long-term observations has given scientists similarly high confidence that they have been impacted by regional climate change.

— Robbins et al., “Baseline monitoring of the Western Arctic Ocean estimates 20% of Canadian Basin surface waters are undersaturated with respect to aragonite,” PLoS ONE — This team discovered a disturbing connection between sea ice melt in the Arctic and ocean acidification. Data collected on concentrations of aragonite (a mineral that is critical to the survival of calcium carbonate-dependent species such as conch) in Western Arctic Ocean surface waters indicate decreasing availability. Authors attribute the change to increased CO2 absorption by sea water and the addition of fresh water from melting ice.

— Santer et al., “Human and natural influences on the changing thermal structure of the atmosphere,” Proceedings of the National Academy of Sciences — This study further demonstrates that human activities, such as greenhouse gas pollution, are the primary drivers of modern warming trends. This is the first study to combine all major natural forces into a comprehensive set of simulations of “climate without humans,” and then to ask whether observed climate trends could be plausibly explained by natural factors only.

— Stanton et al., “channelized ice melting in the ocean boundary layer beneath Pine Island Glacier, Antarctica,” Science — Research found that warm ocean water — rather than warm air — caused increased melting of Pine Island Glacier’s floating ice shelf in Antarctica. In addition to demonstrating one of the side effects of global ocean warming, the study also forewarns of further sea level rise. 

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