Current global climate change effects include increased global surface temperatures, a rise in global sea levels, altered precipitation patterns, and thawing of sea ice and glaciers. Assessments of climate change are most reliable for the past fifty years — during which accurate data has been systematically gathered all over the globe and throughout the upper atmosphere.18 For data on the climate in the distant past, scientists rely on a variety of sophisticated methods including using coral reefs, pollen samples drawn from lake beds, and arctic glaciers to ascertain climate conditions.
While temperatures around the world have risen, it is important to note that temperature changes have not been uniform. Some areas will and are getting colder, but trends in the mean land and ocean temperature have increased by 1° C, nearly 2° F in the past hundred years.19 While seemingly minor, warming of 3° F is enough to reduce crop yields significantly. Projected temperature increases in tropical areas would reduce important calorie rich staple crops by 20-40%, a reduction that would dramatically increase malnutrition levels in many of the world’s poorest countries.20 Areas around the equator will be particularly hard hit by climate change. Regions such as the Middle East and Northern Africa are predicted to see their temperatures increase by over 6° F by the end of the century.21 These increased temperatures will affect everything from sea levels, to fresh water availability, to sanitation, to the spread of disease.
The increase in temperatures has caused sea ice to melt beyond seasonal thaws and glaciers to shrink. The Arctic is particularly affected by the increase in temperature and its melting ice contributes to climate change. Scientists looking at long-term trends believe that sea ice is declining by 3.3% per decade, or 15,500 square miles each year.22 Arctic sea ice reflects sunlight and helps moderate the global climate. As it melts, it produces a vicious cycle of increased warming leading to further reductions in sea ice.
Ice on land surfaces also melts as temperatures warm. The melting ice will increase sea levels and coastal erosion, which also contributes to further erosion of continental ice shelves. Similar to global temperatures, global sea levels have risen, although not uniformly, by roughly eight inches in the past 100 years.23
Rising sea levels in combination with expected changes in precipitation will affect access to fresh water. As temperature increases, demand for fresh water to irrigate crops will increase and place further stress on limited fresh-water sources. As a result, the salinity of water will increase, threatening its suitability for irrigation or human consumption. This frequently results in migration to areas already environmentally stressed, where the cycle is then repeated — highlighting the fact that climate change often begets further climate change.