Climate Analysis

The goal of climate analysis is to better understand the Earth’s past and present climate, and to predict future climate response to changes in natural and human-induced factors, such as the Sun, greenhouse gases (e.g., water vapor, carbon dioxide and methane), and aerosols (e.g., from dust storms, pollution, fires, sea spray or volcanic eruptions). Climate analysis studies are routinely carried out using a mix of data from diverse sources including historical climate data, current and past satellite instruments, field campaigns, and outputs from regional and global numerical models.

The energy budget of the Earth is determined by the energy input from the Sun, what fraction of it is reflected and absorbed by the Earth system, and thermal emission from the Earth itself. Laboratory scientists study the total solar irradiance at the top of the atmosphere using satellite measurements, as well as the solar irradiance at the Earth’s surface using pyranometers and other ground-based instruments. Long-term, homogeneous measurements of both quantities play a crucial role in climate research. The end goal of these studies is to produce more accurate datasets for detecting changes in the energy balance across the globe. This in turn would allow us to more accurately understand changes in the Earth’s radiative forcing and to study the subsequent response and variability of the climate system.

Lab scientists use direct observations, model analyses, and various satellite measurements to study the variability of the global hydrologic (water) cycle, including changes in the distribution of water vapor, precipitation, evaporation, and moisture transport as affected by naturally occurring climate fluctuations such as the El Nino Southern Oscillation (ENSO), the quasi-biennial oscillation (QBO), and others. Variations in rainfall and cloud characteristics, as well as the occurrence of extreme rainfall associated with sea surface temperature change, are being studied using Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Climatology Project (GPCP) rainfall data in conjunction with outputs from global numerical Earth-system models.

Aerosols are now recognized as a key element of the climate system. Aerosols can both cool the Earth’s surface by reflecting light back into space and heat the atmosphere by absorbing sunlight. Aerosols also interact with clouds and modify them in a way that can lead to further changes in the energy budget. When deposited on snowy surfaces, aerosols affect snow reflectivity and the melting processes. Lab scientists study the effect of aerosols on the atmospheric water cycle, particularly over highly populated monsoon regions where large concentrations of natural and anthropogenic (human-produced) aerosols are encountered. Using satellite measurements of aerosol loading, snow, temperature, and rainfall, combined with model reanalysis data, Lab scientists investigate aerosol-induced changes in atmospheric circulation, snow cover, temperature, and rainfall. They also study the long-term variation of atmospheric aerosol loading, intercontinental transport of aerosols, and potential long-term changes in surface air pollution and their effects.

An issue that makes climate research both interesting and challenging is the blending of physical processes whose evolution in time can be predicted well into the future, with others not so easily predicted. Comparisons of observations about the Earth's climate with models of how the climate is evolving must take into account this inherent lack of predictability, sometimes referred to as “climate noise”. Much of climate data analysis deals with the separation of climate signals from noise. Methods have been developed to filter out climate noise from signal, using optimal weighting of observations and simplified models of the climate system to compare climate change predictions with observed changes. Such lines of research are actively pursued by Lab scientists.

Contact: Kyu-Myong Kim