21-3 Climate Change and Human Activities

How Have Human Activities Affected Tropospheric Concentrations of Greenhouse Gases? Messing with the Carbon Cycle

According to the 2007 IPCC report, three human activities have emitted large amounts of greenhouse gases into the troposphere at a faster rate than natural processes can remove them.

One has been the sharp rise in the use of fossil fuels, which release large amounts of CO2 and CH4 into the troposphere. Electricity generated by coal is responsible for about 42% of this input, transportation 24%, industrial processes 20%, and residential and commercial uses 14%.

A second process is deforestation and clearing and burning of grasslands to raise crops and build cities, which release CO2 and N2O. Third is the raising of an increasing number of cattle and other livestock that release methane as a result of their digestive processes. A fourth process is cultivation of rice in paddies and use of inorganic fertilizers that release N2O into the troposphere.

Which Country Is the Largest Greenhouse Gas Emitter? No Longer the United States

Until 2006, the United States was the world’s largest emitter of CO2, followed by China, the European Union (consisting of 27 countries), Indonesia, Russia, Japan, and India. However, according to a number of studies (Gregg et al., 2008; NEAA, 2008), China’s fast-growing coal-intensive economy began to produce CO2 in greater quantities than the U.S. economy in 2006. China has been producing large amounts of CO2 for a relatively short time and is estimated to have contributed about 5% of the world’s cumulative CO2 emissions, compared to 25% generated by the United States. Furthermore, China’s CO2 emissions represent that of a population that is about four times the size of the U.S. population.

Is the Troposphere Warming? Very Likely

Here are five of many 2007 IPCC findings that support the scientific consensus that it is very likely (90–99% probability) that the troposphere is getting warmer. First, the 20th century was the hottest century in the past 1 000 years. Second, since 1861 the average global temperature of the troposphere near the Earth’s surface has risen 0.7°C (1.3°F) over the entire globe and about 0.8°C (1.4°F) over the continents. Most of this increase has taken place since 1980. Third, 11 of the 12 years from 1995–2006 rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850), and the temperature increase has been greatest at high northern latitudes. Fourth, glaciers and floating sea ice in many parts of the world are melting and shrinking. Fifth, during the last century the world’s average sea level rose by 0.1–0.2 metre (4–8 inches), partly from runoff from melting ice and partly because the volume of ocean water expands when its temperature increases

The terms global warming and global climate change are often used interchangeably but they are not the same. Global warming refers to temperature increases in the troposphere, which in turn can cause climate change. Global climate change is a broader term that refers to changes in any aspects of the Earth’s climate, including temperature, precipitation, and storm intensity. It can involve global warming or cooling, but our focus will be on global warming. Global warming should not be confused with the problem of ozone depletion.