Climate Change 101

What is climate change?

Climatologists at the National Oceanic and Atmospheric Administration (NOAA) define the terms weather and climate as:

image of lightning
  • Weather is the state of the atmosphere at a particular time, as defined by variables such as temperature, precipitation or winds.
  • Climate is the "average weather" over a period ranging from months to thousands or millions of years.

Weather can be thought of as current conditions; whereas climate refers to a pattern of weather over time. Climate change is a departure from the expected average weather patterns, which are also known as the "climate normal."

image of the arctic ocean

Climate change may result from:

  • Natural factors, such as changes in the sun's intensity or slow changes in the Earth's orbit around the sun.
  • Natural processes within the climate system (e.g., changes in ocean circulation).
  • Human activities that change the atmosphere's composition (e.g., through burning fossil fuels) and the land surface (e.g., deforestation, reforestation, urbanization, desertification, etc.).

Three major concerns raised by the last few decades of observations include the following:

  1. The rate of change is unprecedented in recent history (IPCC, 2013)
  2. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century (IPCC, 2013)
  3. Changes will likely have consequences on the health of the public (NCA, 2013)

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Climate Change in Minnesota

According to the Minnesota State Climatology Office and Dr. Mark Seeley, there are three recent significant climate trends in Minnesota:

  1. The average temperature is increasing.
  2. The average number of days with a high dew point is increasing.
  3. The quantity and character of precipitation is changing.

The average temperature is increasing.
Temperature has been rising in Minnesota. According to the Minnesota State Climatology Office, Minnesota's average temperature changed very little from 1891 (the start of the National Weather Service record) to the early 1980s. The chart below shows Minnesota's annual average temperature (in red), which demonstrates the wide fluctuation in temperature from year to year, and the 10-year running average temperature (in blue) from the late 1890s to 2010. The 10-year running average temperature (in blue) shows an upward trend in temperature starting in the 1980s.

chart of temperature trends in minnsota from 1890 to 2010

Three significant trends in this overall warming (from Observing the Climate, former State Climatologist Jim Zandlo):

  1. Winters temperatures have been rising about twice as fast as annual average temperatures.
  2. Minimum or 'overnight low' temperatures have been rising faster than the maximum temperature.
  3. Since the early 1980s, the temperature has risen slightly over 1°F in the south to a little over 2°F in much of the north; the trend has been upward.

The average number of days with a high dew point is increasing.
"The dew point temperature is the temperature to which the air must be cooled at constant pressure for it to become saturated. The higher the dew point is, the more uncomfortable people feel. This is because people cool themselves by sweating and if the dew point is at a high temperature, then it becomes more difficult for sweat to evaporate off the skin." (Minnesota State Climatology Office)

In recent decades, Minnesota has seen increasing number of days with high dew point temperatures. The chart below shows the trend line (dashed red line) of the number of days where the maximum dew point was greater than or equal to 70°F in the Twin Cities from 1945 to 2010. The slope of the trend line suggests that there has been an increase in .53 days with a dew point greater than or equal to 70°F per decade.

chart of dew point temperature trends in minnsota from 1945 to 2010 Source: Dr. Mark Seeley, Climatologist, University of Minnesota

Prior to 2011, the highest dew point temperature ever recorded in the Twin Cities was 81° on July 30, 1999. On July 19, 2011 the dew point temperature reached 82° in the Twin Cities and a state record maximum of 88° in Moorhead, Minnesota.

A high dew point combined with high air temperatures creates dangerous extreme heat events. Extreme heat events can cause a range of health effects, from heat rashes to deadly heat stroke. Heat exposure also can aggravate several chronic diseases, including cardiovascular and respiratory diseases. (CDC, Climate and Health)

The quantity and character of precipitation is changing.
The quantity and character of precipitation in Minnesota is changing. Overall precipitation has increased since the Dust Bowl era of the 1930s. The chart below shows Minnesota's average annual precipitation (in red), which demonstrates the wide fluctuation in precipitation from year to year, and the 10-year running average precipitation (in blue) from the late 1890s to 2010. The 10-year running average precipitation (in blue) shows an upward trend in precipitation from the 1930s.

chart of precipitation trends in minnsota from 1890 to 2010

Annual precipitation is expected to continue to increase. Additionally, Minnesota is starting to experience increases in localized, heavy precipitation events. The new precipitation trends have the potential to cause both increased flooding and drought, based on the localized nature of storms and their intensity, leaving some areas of the state drenched and other areas without any precipitation. For example, in August 2007, 24 counties throughout Minnesota were included in a US Department of Agriculture (USDA) drought disaster declaration while at the same time seven southeastern counties were declared a federal flood disaster by the Federal Emergency Management Agency (FEMA).

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Climate Change 101 Training Module

image of the climate change and public health module cover page Climate and weather impact human health, with events such as regular spring floods, seasonal drought, tornados, or freezing winters with blizzards. Recently, scientists and climate experts have reached consensus that the climate is changing and will likely bring increasingly frequent and severe heat waves and extreme weather events. These changes will affect human health.

MDH developed the Climate Change and Public Health 101 Training Module to provide an overview of the most likely climate changes in Minnesota and their potential impacts on public health. This module may be used as an educational piece for interested persons or as a "train the trainer" module for local public health departments. The training has been fully scripted for that purpose.



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Updated Tuesday, 21-Jan-2014 07:33:54 CST