Weather data and observations in the Northern Plains serve as an example of climatic changes that are taking place. Summer surface temperatures of Lake Superior, the largest freshwater lake in the world by surface area, have increased about 4.5 degrees since 1979, compared with about a 2.7-degree increase in the region’s annual average air temperature.  That’s according to a recent study by University of Minnesota Duluth Large Lakes Observatory and Department of Physics, based on data collected by National Oceanic and Atmospheric Administration buoys on the lake, and on 102 years’ worth of daily temperature readings at a hydroelectric plant near Sault Ste. Marie, Mich. 

According to the study, the lake’s “summer season” is now beginning about two weeks earlier than it did 27 years ago, and its ice cover could completely vanish by 2040.  Study authors say that as a result, water levels could drop sharply, since the lake loses more water to evaporation in a winter without ice cover than it does during the summer.  Even in recent months, say the study’s authors, the lake’s level has been lower than at any equivalent time since 1926.

The warmth up north isn’t confined to Minnesota. Since 1990, Fargo, N.D., has posted seven of its 10 highest average annual temperatures, increases consistent with higher average temperatures catalogued in many places throughout the world.

Perhaps you heard that the National Arbor Day Foundation released a new U.S. Hardiness Zone Map (online at www.arborday.org), which reflects the many areas of the country that have become warmer since 1990, when the last USDA hardiness zone map was published. Significant portions of many states have shifted at least one full hardiness zone in the new hardiness map. Areas of southern South Dakota and southern Minnesota have shifted from Zone Four to Zone Five.  Areas of Minnesota, Montana and North Dakota climbed from a Zone Three to Zone Four.

The Pew Center on Global Climate Change has good background on this issue at www.pewclimate.org  — see the information under “Global Warming Basics” and “Climate Change 101.” The most comprehensive and authoritative source on this issue, however, is the Intergovernmental Panel on Climate Change, established in 1988 by the World Meteorological Organization and the United Nations as a global-warming science review body.

The IPCC’s most recent Assessment Report on climate change, being released over the course of 2007, is the most comprehensive yet, involving more than 450 lead authors, 800 contributing authors and 2,500 scientific expert reviewers in three working groups representing more than 130 countries.  An analysis of mitigation options and strategies for the short and long term was released on May 4, and an overall summary will be released on November 16.

Key details of the most recent data can be found on the IPCC Web site (www.ipcc.ch) in the “Summary for Policymakers” under the “Working Group” reports.  The most vulnerable industries, settlements and societies, according to the IPCC, are generally those in coastal and river flood plains, those whose economies are closely linked with climate-sensitive resources, and those in areas prone to extreme weather events, especially where rapid urbanization is occurring.

Approximately 20 to 30 percent of plant and animal species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5 to 2.5 degrees Centigrade, according to the IPCC.

Globally, crop productivity is projected to increase slightly at mid- to high latitudes for local mean temperature increases of up to 1 to 3 degrees Centigrade, depending on the crop, and then decrease beyond that in some regions.  At lower latitudes, especially seasonally dry and tropical regions, crop productivity is projected to decrease for even small local temperature increases of one to two degrees Centigrade.

Agricultural production, including access to food, in many African countries and regions is projected to be severely compromised by climate variability and change. By 2020, 75 million to 250 million people are projected to be exposed to an increase of water stress due to climate change. If coupled with increased demand, this will adversely affect livelihoods and exacerbate water-related problems.

In North America, moderate climate change in the early decades of the century is projected to increase aggregate yields of rain-fed agriculture by five to 20 percent, but with variability among regions. Increases in the frequency of droughts and floods are projected to affect local crop production negatively, especially in subsistence sectors at low latitudes.

The IPCC projects major challenges for crops that are near the warm end of their suitability range or depend on highly utilized water resources.  “Adaptations such as altered cultivars and planting times will allow low- and mid- to high-latitude cereal yields to be maintained at or above baseline yields for modest warming,” the IPCC says.

In related work, if they find funding for the research, University of Minnesota crop scientists hope to assess the influence of climate change on grain production in the state and how crop breeding programs and cropping systems may need to change.

A mix of strategies that includes mitigation and adaptation is needed to address the effects of climate change, suggests the IPCC, “combining policies with incentive-based approaches, and actions at all levels from the individual citizen through to national governments and international organizations.”

Tracy Sayler is an ag writer based near Fargo, N.D.