The science is clear — the world's climate is changing

Illinois has already seen the impacts on everything from agriculture productivity and food access to public health hazards and diminishing natural resources. Weather patterns have shifted significantly in the past century, with Illinois dealing with both warmer temperatures and more precipitation, according to the Prairie Research Institute’s Illinois State Climatologist office.

Intense rainfalls have led to increased urban and rural flooding as well as more frequent summer drought stress and the potential for water shortages. Illinois has also experienced more warming during the winter and transition seasons and very little warming during the summer. Despite summer not “warming,” humidity has increased in the Midwestern U.S., leading to an increase in human heat stress.  

Report on Climate Change in Illinois

How has climate changed over time?

In the last 3 million years, climate has gone between tens of thousands of years of cooling followed by a much shorter warming period. Today's rapid warming is happening 20 times faster than our historical pace. The causes are both natural- and human-based. The consequences of a hotter earth are substantial.
 

Nature impacts climate over time

• Land masses changing position through tectonic plate movement
• Changes in ocean currents (also due to plate movement)
• Changes in solar energy received by the earth due to slight changes in the earth's orientation and distance from the sun
• Very long volcanic events lasting millions of years
• Short-term changes from brief volcanic events and meteorite impacts

The cooling periods created huge sheets of ice that covered much of North America, Europe, and Asia, and to a lesser extent, the southern hemisphere. The current theory on the cause of ice ages relates to changes in the earth's tilt, distance from the sun, and the wobble of its axis. All of these slowly change over tens of thousands of years and correlate closely to when ice ages occur.
 

Enhanced warming of the earth’s lower atmosphere is affecting that natural cycle.

“Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5,000 years to warm 5 degrees. The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual." 
- NASA Earth Observatory