CAS Research

The mission of the Climate Analysis Section is to increase the understanding of the atmosphere and climate system through empirical studies and diagnostic analyses of the atmosphere and its interactions with the Earth's surface and oceans on a wide range of scales with a particular goal of contributing to the building of a climate information system.

Emphasis of research is on the atmospheric and oceanic general circulations, meteorological phenomena such as tropical cyclones, global warming, the hydrological cycle, and climate variations over several time scales. Research has focused on interannual variations, such as the El Nino-Southern Oscillation and the North Atlantic Oscillation phenomena; decadal variations, such as the Pacific Decadal Oscillation; and longer-period trends, and their climate forcings. Attribution and mitigation of climate change are also topics of in-depth research.

Highlights

What's With This Weather? Brrr: The AO is way low. No matter how you slice it, the last few weeks have been consistently wintry across large chunks of North America and Eurasia. "Most winters are not dominated by any particular regime," note Hurrell and Deser in a recent overview of the NAO for the Journal of Marine Systems. In other words, February could flip into a positive NAM mode just as easily as it could stay largely negative. Staff: Clare Deser and James Hurrell. [highlight] [study] [CAS]

Climate change and other factors are drying up many of the world's rivers.
Many of the world's big rivers are drying out, with no sign of relief. Kevin Trenberth of the National Center for Atmospheric Research and his colleagues analyzed 925 rivers around the globe, from 1948 to 2004. Trenberth says a third of these rivers showed significant changes. And the majority of those that changed have gotten drier. [radio interview]

Press Release: 21 April 2009
Water Levels Dropping in Some Major Rivers as Global Climate Changes
Rivers in some of the world's most populous regions are losing water, according to a new comprehensive study of global stream flow. The study suggests that in many cases the reduced flows are associated with climate change. Staff: A. Dai and K. Trenberth

First International Meeting on Attribution of Climate Events
To kick off the ACE activity, a one day meeting was held at NCAR on 26 January 2009 to discuss the research needed to provide authoritative assessments of the causes of anomalous climate conditions and extreme weather events.
Staff: A. Dai, C. Deser, J. Hurrell, and K. Trenberth

Recent Publications

Simulation of present day and 21^st century energy budgets of the southern oceans. Trenberth, K.E. and J.T. Fasullo. 2010: Journal of Climate, 23, 440-454, doi:10.1175/2009JCLI3152.1.
The energy budget of the modern-day southern hemisphere is poorly simulated in both state-of-the-art reanalyses and coupled global climate models. The ocean-dominated southern hemisphere has low surface reflectivity and therefore its albedo is particularly sensitive to cloud cover. [article]

Global warming due to increasing absorbed solar radiation
Global climate models used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) are examined for the top-of-atmosphere radiation changes as carbon dioxide and other greenhouse gases build up from 1950 to 2100. There is an increase in net radiation absorbed, but not in ways commonly assumed. [article] [abstract]