THE SCIENCE OF CLIMATE CHANGE: A LOOK AT OUR CHANGING LANDSCAPE

The science is clear—the climate on our planet, including the United States, is changing, changing much more rapidly than occurs naturally, and it is happening primarily because of human activities, especially from our use of fossil fuels but also from land use change. Evidence for a changing climate abounds, from the top of the atmosphere to the depths of the oceans. Documented changes include surface, atmospheric, and oceanic temperatures; melting glaciers; disappearing snow cover; shrinking sea ice; and rising sea level. Severe weather is becoming more intense. Temperature extremes and heatwaves have become more frequent since the 1960s, while extreme cold temperatures and cold waves are less frequent. Heavy rainfall is increasing in intensity and frequency globally. All of these trends are expected to continue. Decreasing ice, rising sea levels, and increasing intensity of severe weather are likely to have a significant effect on the landscape of our planet over this century and beyond. Humanity is already feeling the effects of the changes in extreme weather and in sea level rise. Many sectors of our society are being affected, including threats on human health and well-being. The United States is seeing effects from the changing climate and these effects are likely to continue and get significantly larger in the future, affecting the people that live and work here. But there is hope—the science also shows that the extent of future effects on human society depend on how we act to limit climate change and our response to potential impacts.