Soil and Climate Change
Effects of Climate Change
Climate change has the potential to adversely impact agricultural productivity at local and regional scales through alterations in rainfall patterns, more frequent occurrences of climate extremes (including high temperatures or drought), altered patterns of pest pressure, and changes in seasonal and diurnal temperature patterns.
Weather versus Climate
Weather is the state of the atmosphere at any given time and place. Most of the weather that affects people, agriculture, and ecosystems takes place in the lower layer of the atmosphere. Familiar aspects of weather include temperature, precipitation, clouds, and wind that people experience throughout the course of a day. Severe weather conditions include hurricanes, tornadoes, blizzards, and droughts. Climate is the long-term average of the weather in a given place. While the weather can change in minutes or hours, a change in climate is something that develops over longer periods of decades to centuries. Climate is defined not only by average temperature and precipitation but also by the type, frequency, duration, and intensity of weather events such as heat waves, cold spells, storms, floods, and droughts.
Climate Change Impact on Precipitation
Annual precipitation since the beginning of the last century has increased across most of the northern and eastern U.S. and decreased across much of the southern and western U.S. Increasing evaporative demand owing to rising temperatures and longer growing seasons could increase crop irrigation requirements and may increase the frequency of water shortages and lead to more restrictions on water usage.
Climate Change Impact on Temperature
Annual temperature over the contiguous U.S. have increased over the last few decades. Additional increases in annual average temperature are projected over the next few decades regardless of future emissions. Elevated temperatures play a critical role in increasing the rate of drought onset, overall drought intensity, and drought impact through altered water availability and demand.
Climate Change and Extreme Weather Events
Average temperature and precipitation are not the only factors that affect agricultural systems. Extreme climate conditions, such as dry spells, sustained droughts, and heat waves can have large effects on crops and livestock. Changes in the incidence of these extreme events could thus have major effects on U.S. agricultural productivity and profitability. Although models are limited in their ability to accurately project the occurrence and timing of individual extreme events, observations indicate an emerging signal that is consistent with projections of an increase in areas experiencing droughts and the occurrence of more intense precipitation events. Historically, many of the largest falls in crop productivity have been attributed to anomalously low precipitation events. However, even small changes in mean annual rainfall can impact on productivity. Many extreme temperature conditions are becoming more common.
Causes of Climate Change
The causes of climate change with both natural and human drivers are discussed below.
Natural Drivers
Climate changes happen for a variety of reasons. Some of these reasons have to do with Earth’s atmosphere. The climate change brought by El Niño, which relies on winds and ocean currents, is an example of natural atmospheric changes. Natural climate change can also be affected by forces outside Earth’s atmosphere. For instance, the 100,000-year cycles of ice ages are probably related to changes in the tilt of Earth’s axis and the shape of its orbit around the sun.
Human Causes
Human-caused global warming is often called anthropogenic climate change. Since the Industrial Revolution, human activities have released large amounts of carbon dioxide and other greenhouse gases into the atmosphere, which has contributed to a change in the earth’s climate. Virtually all climate scientists agree that this increase in heat-trapping gases is the main reason for the rise in global average temperature since the late nineteenth century. Carbon dioxide, methane, nitrous oxide, ozone, and various chlorofluorocarbons are all human-emitted heat-trapping gases. Among these, carbon dioxide is of greatest concern to scientists because it exerts a larger overall warming influence than the other gases combined.
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