climatechange.procon.orgClimate Change - Pros & Cons - ProCon.org

Climate Change - Pros & Cons - ProCon.org Skip to content More Issues About Us FAQs Teachers’ Corner Join Climate Change Is Human Activity Primarily Responsible for Global Climate Change? Last updated on: 5/13/2019 | Author: ProCon.org Temperatures on earth have increased approximately 1.8°F since the early 20th century. Over this time period, atmospheric levels of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) have notably increased. Both sides in the debate surrounding global climate change agree on these points. The pro side argues rising levels of atmospheric greenhouse gases are a direct result of human activities such as burning fossil fuels, and that these increases are causing significant and increasingly severe climate changes including global warming, loss of sea ice, sea level rise, stronger storms, and more droughts. They contend that immediate international action to reduce greenhouse gas emissions is necessary to prevent dire climate changes. The con side argues human-generated greenhouse gas emissions are too small to substantially change the earth’s climate and that the planet is capable of absorbing those increases. They contend that warming over the 20th century resulted primarily from natural processes such as fluctuations in the sun’s heat and ocean currents. They say the theory of human-caused global climate change is based on questionable measurements, faulty climate models, and misleading science. Read more background… Pro & Con Arguments Pro 1 Overwhelming scientific consensus says human activity is primarily responsible for global climate change. The 2010 Anderegg study found that 97-98% of climate researchers publishing most actively in their field agree that human activity is primarily responsible for global climate change. The study also found that the expertise of researchers unconvinced of human-caused climate change is "substantially below" that of researchers who agree that human activity is primarily responsible for climate change. [ 7 ] The 2013 Cook review of 11,944 peer-reviewed studies on climate change found that only 78 studies (0.7%) explicitly rejected the position that humans are responsible for global warming. [ 1 ] A separate review of 13,950 peer-reviewed studies on climate change found only 24 that rejected human-caused global warming. [ 5 ] A survey by German Scientists Bray and Von Storch found that 83.5% of climate scientists believe human activity is causing "most of recent" global climate change. [ 172 ] A separate survey in 2011 also found that 84% of earth, space, atmospheric, oceanic, and hydrological scientists surveyed said that human-induced global warming is occurring. [ 6 ] Read More Pro 2 Rising levels of human-produced gases released into the atmosphere create a greenhouse effect that traps heat and causes global warming. As sunlight hits the earth, some of the warmth is absorbed by greenhouse gases in the atmosphere such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (NO2). These gases trap heat and cause the planet to warm through a process called the greenhouse effect. [ 8 ] Since 1751 about 337 billion metric tons of CO2 have been released into the atmosphere from the burning of fossil fuels and cement production, [ 9 ] increasing atmospheric CO2 from the pre-industrial level of about 280 ppm (parts per million), to a high of 400 ppm in 2013. [ 10 ] Methane, which is increasing in the atmosphere due to agriculture and fossil fuel production, traps 84 times as much heat as CO2 for the first 20 years it is in the atmosphere, [ 11 ] and is responsible for about one-fifth of global warming since 1750. [ 12 ] Nitrous oxide, primarily released through agricultural practices, traps 300 times as much heat as CO2. [ 13 ] Over the 20th century, as the concentrations of CO2, CH4, and NO2 increased in the atmosphere, [ 13 ] [ 14 ] the earth warmed by approximately 1.4°F. [ 99 ] Read More Pro 3 The rise in atmospheric CO2 over the last century was clearly caused by human activity, as it occurred at a rate much faster than natural climate changes could produce. Over the past 650,000 years, atmospheric CO2 levels did not rise above 300 ppm until the mid-20th century. [ 100 ] Atmospheric levels of CO2 have risen from about 317 ppm in 1958 to 415 ppm in 2019. [ 10 ] [ 194 ] CO2 levels are estimated to reach 450 ppm by the year 2040. [ 15 ] According to the Scripps Institution of Oceanology, the "extreme speed at which carbon dioxide concentrations are increasing is unprecedented. An increase of 10 parts per million might have needed 1,000 years or more to come to pass during ancient climate change events." [ 17 ] Some climate models predict that by the end of the 21st century an additional 5°F-10°F of warming will occur. [ 16 ] Read More Pro 4 The specific type of CO2 that is increasing in earth’s atmosphere can be directly connected to human activity. CO2 produced by burning fossil fuels such as oil and coal [ 18 ] can be differentiated in the atmosphere from natural CO2 due to its specific isotopic ratio. [ 101 ] According to the Intergovernmental Panel on Climate Change (IPCC), 20th century measurements of CO2 isotope ratios in the atmosphere confirm that rising CO2 levels are the result of human activity, not natural processes such as ocean outgassing, volcanic activity, or release from other "carbon sinks." [ 102 ] US greenhouse gas emissions from human activities in 2012 totaled 6.5 million metric tons, [ 19 ] which is equivalent to about 78.3 billion shipping containers filled with greenhouse gases. [ 20 ] Read More Pro 5 Average temperatures on earth have increased at a rate far faster than can be explained by natural climate changes. A 2008 study compared data from tree rings, ice cores, and corals over the past millennium with recent temperature records. The study created the famous "hockey stick" graph, showing that the rise in earth's temperature over the preceding decade had occurred at a rate faster than any warming period over the last 1,700 years. [ 23 ] In 2012 the Berkeley scientists found that the average temperature of the earth’s land increased 2.5°F over 250 years (1750-2000), with 1.5°F of that increase in the last 50 years. [ 21 ] Lead researcher Richard A. Muller, PhD, said "it appears likely that essentially all of this increase [in temperature] results from the human emission of greenhouse gases." [ 22 ] In 2013, a surface temperature study published in Science found that global warming over the past 100 years has proceeded at a rate faster than at any time in the past 11,300 years. [ 3 ] According to the IPCC’s 2014 Synthesis Report, human actions are "extremely likely" (95-100% confidence) to have been the main cause of 20th century global warming, and the surface temperature warming since the 1950s is "unprecedented over decades to millennia." [ 24 ] Read More Pro 6 Natural changes in the sun’s activity cannot explain 20th century global warming. According to a Dec. 2013 study in Nature Geoscience , the sun has had only a "minor effect" on the Northern Hemisphere climate over the past 1,000 years, and global warming from human-produced greenhouse gases has been the primary cause of climate change since 1900. [ 26 ] Another 2013 study found that solar activity could not have contributed to more than 10% of the observed global warming over the 20th century. [ 27 ] Measurements in the upper atmosphere from 1979-2009 show the sun's energy has gone up and down in cycles, with no net increase. [ 28 ] According to a 2013 IPCC report, there is "high confidence" (8 out of 10 chance) that changes in the sun's radiation could not have caused the increase in the earth's surface temperature from 1986-2008. [ 29 ] Although warming is occurring in the lower atmosphere (troposphere), the upper atmosphere (stratosphere) is actually cooling. If the sun were driving global warming, there would be warming in the stratosphere also, not cooling. [ 103 ] Read...