Climate Change Basics

Climate Change Trends

CC trendsClimate change is already creating problems for both human and natural systems.

Scientists have documented changes in:

    • Temperature
    • Sea level
    • Heat waves
    • Severe storms
    • Precipitation
    • Wildfire
    • Snow pack
    • Species distribution

    While each and every extreme event can’t be blamed on climate change, the frequency and severity of such events are both increasing over time. A useful analogy is the recent uptick in the use of steroids in professional baseball – can you attribute any single home run to the use of steroids? Not really. Climate change is basically the climate – on steroids.

    Climate change is already being felt worldwide

    Separating Human and Natural Influences on Climate

    These climate shifts have significantly affected human communities and the natural resources they rely upon. Consider the evidence:

    • Atmospheric carbon dioxide has increased 40% in past 100 years.
    • Global average temperature has increased 1.5°F in the past century.
    • Heavy downpours have become more common in the past 50 years, causing more floods, crop damage, and costs to communities.
    • The frequency of heat waves has increased since 1950. Heat waves cause the greatest number of deaths of any natural disaster in the U.S.
    • Wildfire number and size have increased since mid-1980s, with total area burned up 650% (regardless of fire suppression history).
    • Average wildfire season has increased in length from 5 weeks to 7 weeks. 
    • Sea surface temperature has warmed 0.8°F since 1971.
    • Arctic sea ice has melted dramatically since 1978.
    • Sea level rose 8 inches during the 20th century.
    • Ocean acidification has increased over the last 100 years, resulting in a 26% increase in hydrogen ion concentrations.
    • Plants and animals in many areas have moved toward the poles and to higher elevations. Others, such species that already live at high elevations, have decreased in population in response to changing conditions. Some generalist or invasive species have increased in numbers due to more favorable conditions or loss of competitors. 
    • Crop yields have declined in many years due to unusual climate-related events

    Future changes will happen even faster

    Climate change is expected to accelerate in the coming century. While CO2 has increased 40% during the last century, it is expected to increase 300% by the end of the current century. We’ve only begun to feel the impacts, so get ready for the ride. Here are some projections.

    • Global temperature is likely to rise by 3.6 to 11.5°F.  Most areas of North America will exceed that average.
    • Sea level is projected to rise 3 to 10 feet due to thermal expansion of oceans and glacier melt. There is a potential for up to 25 feet of further rise due to ice sheet collapse.
    • Storm events are likely to become more extreme, with precipitation less frequent but more intense.
    • Drought will be more prevalent. By about 2050, average conditions in much of the Western United States will mimic those experienced rarely during the height of the most severe historic droughts.
    • Wildfire patterns will be influenced by rising temperatures and shifting rainfall patterns. Some areas, including much of the western United States, likely will be more prone to uncharacteristically severe fire.
    • Snow and ice will continue to decrease. Many areas of the West are expected to have declines in snowpack greater than 80-90% by the end of the century. As snowpack declines, runoff will occur earlier in the spring and streamflow will decline in the late summer. 

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