National Climate Assessment for Illinois

Earlier this year the National Climate Assessment for Illinois was released, tracking the historical changes in temperatures and precipitation in Illinois. You can find the full report for Illinois and other states at the State Climate Summaries website.
Here is Key Message #1

Average annual temperature has increased by about 1°F since the beginning of the 20th century. There has been seasonal variation in this warming, with average spring temperature increasing by about 2°F and average summer
temperature increasing very little. Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century.

Key Message #2

Precipitation in spring and summer has generally been above average over the past two decades, affecting agriculture in both positive (adequate soil moisture) and negative (delays in spring planting) ways. Precipitation in winter and spring is projected to increase, which poses a continuing risk of spring planting delays.

Key Message #3

Severe flooding and drought have occurred periodically in recent years. Future increases in extreme precipitation events and in evaporation rates may increase the intensity of both floods and droughts.

You may notice that two out of the three messages relate to increases in precipitation and especially heavy rainfall events. The graphic I found most compelling was this one for the increasing number of 2-inch rain events with time. The caption explains how this graph was created. The increased frequency in 2-inch rain events seen since the early 1980s lines up very well with my experience and research over the years in Illinois.

Figure 5: The observed number of days with extreme precipitation events (annual number of days with precipitation greater than 2 inches) for 1900–2014, averaged over 5-year periods; these values are averages from 43 available long-term reporting stations. A typical station experiences 1–2 such events each year. The number of extreme precipitation events has been above average since the 1990s. During the most recent 5-year period (2010–2014), Illinois experienced a record high number of events when stations averaged more than 2 events annually. The dark horizontal line is the long-term average (1900–2014) of 1.62 days per year. Source: CICS-NC and NOAA NCEI.

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Volcanoes and Climate in Illinois

When I give talks on climate and climate change, I often get questions about volcanoes and their impact on our climate. The Washington Post had a recent article on the subject, mentioning the famous eruption of Tambora in 1815, which in 1816 led to the year without a summer in the eastern US. It probably had impacts on Illinois but we had no widespread observations in place at the time.

The one I remember the best was Mount Pinatubo. The following summer after that eruption was exceptionally cool across the US and around the world.

Summer 1992 temperature departures from average for the lower 48 states. Shades of green indicate level of coolness. Click to enlarge.

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2014 – Warmest on Record for World, 6th Coldest for Illinois. Wait, What?

I could see this one coming. While Illinois had its 6th coldest year on record, three major groups (Japan, NASA, and NOAA) have noted that 2014 was the warmest year on record. Check out this map from NOAA of the temperature departures for 2014 (red is warmer, blue is cooler). The area from the Great Lakes and southward to the Gulf of Mexico was the only place over land that was colder than average. All the other land masses and most of the ocean surface was warmer than average. In other words, relatively speaking, Illinois was one of the coldest places on earth in 2014.  Continue reading “2014 – Warmest on Record for World, 6th Coldest for Illinois. Wait, What?”

Illinois and Global Temperatures for June-August

Based on the latest updates from the National Climatic Data Center, this summer in Illinois was the 29th coolest. Daytime highs were much cooler than average while the nighttime lows were near-average.

The average maximum temperature in Illinois was 82.3 degrees Fahrenheit, 2.6 degrees below the 1900-2000 base period and the 14th coolest on record.


The average minimum temperature in Illinois was 62.3 degrees F, 0.3 degrees above the 1900-2000 based period.



In contrast to the cool summer in the central US, most of the globe was warmer than average this summer (June-August), according to the National Climatic Data Center. In fact, even in the US, temperatures were significantly warmer in the West than the East.


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