In this series on "Big Fat Planet," we answer reader-submitted questions about Earth's climate. The following is from Dr. Duane Waliser, who specializes in climate dynamics and modeling. He is the chief scientist of JPL's Earth Science and Technology Directorate and an adjunct professor in the Atmospheric and Oceanic Sciences Department at UCLA.

Question: How is climate change shaping the type of space exploration NASA does?

As global climate change becomes more evident, NASA’s satellite program for studying and monitoring our home planet becomes increasingly important. There are two key areas toward which NASA satellite measurements can contribute:

1. Monitoring changes in the Earth’s climate. Global climate change occurs slowly relative to weather and even to the change of seasons throughout the year. Changes known to be related to global climate change--increased atmospheric carbon dioxide and other greenhouse gases (including water vapor), sea level rise, and the melting of Arctic sea ice and the Greenland and Antarctic ice sheets--are so gradual that it takes many years, even decades, to characterize and quantify them.

Given that satellite missions typically last on the order of three to 10 years, NASA often needs to consider launching copies of some instruments, as current versions age and fail. Continuity in our satellite observations is important for maintaining long records of key climate indicators, such as those listed above. Having long and continuous records of these is critical for monitoring the effects of climate change, helping determine how we can best adapt to them, and assessing whether measures to limit its effects are working as expected.

2. Improving our understanding of global climate change key processes. Simply monitoring some of the climate change indicators listed above doesn’t provide enough information for scientists to fully understand and characterize the problem and consequences.

For example, only observing sea level rise doesn’t illuminate all the key processes that might be involved in determining the rate at which it is rising; these include sea level rise, the melting of ice sheets and glaciers, warming of the ocean, the continents’ and shorelines’ slow response to ice sheet melting and sea level rise, etc. Similarly, it is critical to understand how water vapor and clouds respond to climate change, as these help determine the amount of future temperature warming that might be expected to result from increasing the amount of greenhouse gases in the atmosphere.

Knowing "how the Earth’s climate works" is vital to making projections of future warming and the associated impacts using very sophisticated computer models of the Earth’s climate. For such projections to be useful, they have to accurately represent the Earth’s climate system.