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Climate Change Introduction

To explain the difference between weather and climate, scientists often say, "climate is what you expect, weather is what you get."" Climate is the weather of a particular region, averaged over a long period of time. Climate is a fundamental factor in ecosystem health--while most species can survive a sudden change in the weather, such as a heat wave, flood or cold snap--they often cannot survive a long-term change in climate. Global climate is the average of all regional trends, and researchers have concluded that Earth's climate, as a whole, is warming.

Researchers know that human activities including fossil fuel use, agriculture and land use have been the dominant causes of increased concentrations of greenhouse gases in the atmosphere over the past 250 years. In addition, aerosols and land surface changes are also altering the Earth's climate, making it extremely likely1 that human activities have had a net warming effect since 17502. These human-caused changes to the climate system, and their consequences, provide much of the impetus for the National Science Foundation's (NSF) climate change research.

Researchers funded by NSF have discovered signs of a changing climate in nearly every corner of the globe, from the icy expanses of Earth's polar regions to its equatorial ecosystems. Our planet's climate affects--and is affected by--the sky, land, ice, sea, life and the people found on it. To piece together the entire puzzle of climate change--what we know, what we still have to learn and what humankind can do to prepare for the future--we must study all of the physical, natural and human systems that contribute to and interact with Earth's climate system.

As researchers piece together the climate puzzle, they are revolutionizing the way we understand the Earth system as a whole. Researchers have realized that they must reach across disciplinary boundaries to study questions that extend beyond any one field of science or engineering. In fact, because of the complexity of Earth's climate, this research involves contributions from nearly every field of science, math and engineering.

In no area is NSF's contribution more important--or more influential--than in interdisciplinary research. NSF responds to the needs of research communities by supporting teams that include experts from multiple disciplines. NSF is unique among other government agencies with a science mission because NSF funds research, infrastructure and education across all disciplines of science and engineering.

Putting the Pieces Together
The evidence we have for a changing planet goes well beyond any one field of science or engineering.

Ecologists have noted marked changes in the habitats of the species they study--changes in the places where they find a particular species, changes in the dates plants first sprout and bloom, changes in plant growth rates and even signs of evolutionary adaptation brought on by a warming climate. In some cases, species extinctions appear linked to climate change.

Ocean scientists have recorded higher temperatures and higher ocean acidity, which alter the characteristics of the most fundamental organisms of the ocean food chain. Coral reefs--some of which have thrived for centuries--have died off suddenly as a result of ocean temperatures that exceed the corals' ability to survive.

Polar scientists have watched vast tracts of Arctic sea ice melt away, leaving behind more open water than anyone can remember seeing during any previous Northern Hemisphere summer. Glaciologists have witnessed ice shelves--once thought too large to be influenced by anything short of cataclysmic environmental change--break up into a churning sea of icebergs in a matter of days.

Social scientists have recorded the bewilderment of indigenous people. Their cultural knowledge, which stretches back in time through numerous generations, holds no record of the kinds of environmental conditions they are encountering today.

Paleoclimatologists have discovered--through tree ring data, ice cores and other corroborating records--that the concentration of carbon dioxide, and the Earth's average temperature, are nearing levels that haven't been reached for hundreds of thousands of years.

Innovative scientists and engineers have responded to the call for alternative energy sources that reduce the amount of carbon dioxide we put into the atmosphere. Computer scientists are creating new tools for geoscientists, decision-makers and the public to understand Earth's changing climate. Social scientists are studying human decisions and behaviors that influence the environment. By studying such issues as the energy grid, land use, urban planning, building materials and economic factors that are linked to anthropogenic climate change, researchers are beginning to tackle some of the more nuanced, but essential, questions regarding the human impact on, and response to, the Earth's changing climate.

1. According to the Treatment of Uncertainties in the Working Group I Assessment of the Intergovernmental Panel on Climate Change, 'extremely likely' corresponds to a likelihood of >95% probability. Solomon, S., et al. Technical Summary, in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007 Cambridge University Press. Box TS.1

2. Solomon, S., et al. Technical Summary, in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. Cambridge University Press. pp. 81

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