Climate Change Report
August 24, 2008
Climate change is already affecting US water resources, agriculture, land resources and biodiversity, according to a recent report from the US Climate Change Science Program. The report, written by 38 authors from federal service, universities, national laboratories and non-governmental organizations, is one of the most extensive examinations of climate impacts on the US to date.
Though many model projections of climate change project out 100 years, the current study focuses on the nearer term future of 25 to 50 years. Most of the change that will occur during this period is a result of greenhouse gas emissions that have already been released into the atmosphere, and so studying this period fits well into the planning horizon of natural resource managers.
The report determined that warming is likely to continue into the nearer future, and therefore have a significant impact on ecosystem change. In recent years, climate change has already influenced things like erosion, weed growth and the frequency of insects and fires. As temperatures have risen beyond those recommended for optimal growth and reproduction, it has hurt animal and crop production.
These changes are likely to accelerate because climate change leads to a slew of direct and indirect effects on the US ecosystem. The cleaning of water and the natural removal of carbon from the atmosphere is greatly impacted by warming temperatures.
Other consequences include altered bird migrations, increased evaporation, longer growing seasons coupled with increased drought and vulnerability to pests, and changes in water quality. Over the last 19 years, the growing season has increased by 10 to 14 days across temperature latitudes.
Temperature, precipitation, CO2 concentrations and water availability directly influence agriculture. The report found that increased CO2 and temperature will likely speed up the growth of grains and oilseeds, however, climate variability could result in eventual crop failure. More sensitive crops like tomatoes, onions and other fruits are also expected to suffer. Under hotter temperatures, livestock production will probably decrease.
While nitrogen deposition and warmer temperatures have likely increased forest growth in areas where water is still readily available, the combined effect of CO2, ozone and forest disturbance on soil is still unclear. Continued erosion, the proliferation of fire-prone exotic grass species and increased drought will result in more fires, more intense thunderstorms and increased tree mortality.
Interestingly, in terms of water quality and quantity, researchers found that most of the water changes observed across the US are a result of factors unrelated to increased water temperatures or changes in precipitation. And as much of the US has experienced higher precipitation and streamflow, many areas have in turn experienced decreased drought severity and duration.
But overall, the systems in place to detect climate change or its effect on water resources are obsolete and poorly integrated. Increased drought in the West and Southwest, for example, and the trend toward reduced mountain snowpack and earlier spring snowmelt runoff in the Western US are reminders that global warming directly impacts our water supply.
Lastly, climate changes are having an effect on biodiversity, or the variation of life at the genetic, species and ecosystem levels of biological organization. Changes in growing seasons, species distribution and diversity are far reaching. Coral reefs are suffering from bleaching events and increased oceanic acidity. Snow and ice covers are disappearing for polar bears in the Arctic. The disruption of the relationship between pollinators and flowers is a possibility too.
During the 20th century, global average surface temperature increased by about .6 degrees Celsius. Global sea level increased by about 15 to 20 cm. Global average temperature is expected to rise an additional 1.1 to 5.4 degrees Celsius by 2100. Temperatures in the US are likely to increase by 1 degree Celsius.