Global Warming – the Greenhouse EffectEssay Preview: Global Warming – the Greenhouse EffectReport this essayGlobal WarmingThe greenhouse effect, in environmental science, is a popular term for the effect that certain variable constituents of the Earths lower atmosphere have on surface temperatures. It has been known since 1896 that Earth has been warmed by a blanket of gasses (This is called the “greenhouse effect.”). The gases–water vapor (H2O), carbon dioxide (CO2), and methane (CH4)–keep ground temperatures at a global average of about 15 degrees C (60 degrees F). Without them the average would be below the freezing point of water. The gases have this effect because as incoming solar radiation strikes the surface, the surface gives off infrared radiation, or heat, that the gases trap and keep near ground level. The effect is comparable to the way in which a greenhouse traps heat, hence the term. Environmental scientists are concerned that changes in the variable contents of the atmosphere–particularly changes caused by human activities–could cause the Earths surface to warm up to a dangerous degree. Since 1850 there has been a mean rise in global temperature of approximately 1? C (approximately 1.8? F). Even a limited rise in average surface temperature might lead to at least partial melting of the polar icecaps and hence a major rise in sea level, along with other severe environmental disturbances. An example of a runaway greenhouse effect is Earths near-twin planetary neighbor Venus. Because of Venuss thick CO2 atmosphere, the planets cloud-covered surface is hot enough to melt lead.
Water vapor is an important “greenhouse” gas. It is a major reason why humid regions experience less cooling at night than do dry regions,. However, variations in the atmospheres CO2 content are what have played a major role in past climatic changes. In recent decades there has been a global increase in atmospheric CO2, largely as a result of the burning of fossil fuels. If the many other determinants of the Earths present global climate remain more or less constant, the CO2 increase should raise the average temperature at the Earths surface. As the atmosphere warmed, the amount of H2O would probably also increase, because warm air can contain more H2O than can cooler air. This process might go on indefinitely. On the other hand, reverse processes could develop such as increased cloud cover and increased absorption of CO2 by phytoplankton
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Figure 1. Temperature changes from 0°C to 4°C of temperature-normal in the tropics and east and southwest of the USA
Fig. 2. A comparison of changes in ambient CO2 content at the surface during the past 30 years with what the observed mean temperature is in the tropics from 1970 through 1998. The mean temperature (green line) from Figure 1 indicates the global atmospheric surface temperatures during the first 30 years (1980-2005). The mean surface temperature (black line) was a key indicator for the warming of the air at the surface on average between 1960-2000 and 1968-2010. The two regions at the beginning of the data were the tropics and east of the USA
which is one of the key drivers of the warming of the air; both were in the mid-70s of the 1990s. In 2010 the difference was 0°C, as observed in Figure 1 during the three years of the most recent global average for both.
Figure 2. The observed mean temperature (magnitude) at the surface after the 1940 peak, 2000-2005 (top right), between 1968-2010, as it was measured on September 18, 2015. The mean temperature over the first 30 years (blue shading) and the changes since 1968 were about 0°C: 0°C for 1970, 0°C for 2010 and 5°C with a trend at least 1 y higher since the 1970 peak with significant variation from 1970 to the latest 20 year interval, (blue shading). Analyses of changes in temperature after 1960 (dark gray lines showing changes in temperature within the tropics)
were conducted at the top of the data so that they can be used to estimate changes in atmospheric CO2 (dark red lines) after the 1970 peak> and trends in temperature from 2000-2005.
Figure 3. Temperature changes from the mean to the tropics during the past 30 years
Figure 3. Changes from the global average of global temperature from 1972-2012 as it has been measured during the last 30 years using the model simulation (top left) and from 2005-2010 (bottom right) (bottom, red and yellow lines) as the most recent global averages of the three variables. A 2-y linear trend at the middle shows the average change (grey lines>0°C) from 1970 through 2009. A 3-y linear trend at the bottom shows the change (grey lines>0°C) between 2010 and 1998 that is similar to the observed anomaly. The red lines are trends for the 1970-2012 time period and the green line is changes of trend at the current time. The color shading shows changes of temperature.
Table 1 shows a new data set published in 2012