The average air temperature near Earth’s surface has risen about 1.33 degrees Fahrenheit over the past 100 years. The Intergovernmental Panel on Climate Change (IPCC) states that “most of the observed increase in average global temperatures since the mid-20th century is likely due to the observed increase in greenhouse gas concentrations through the greenhouse effect.”
These basic conclusions have been endorsed by at least 30 scientific societies and academics of sciences, including all the national academies of sciences of major industrialized countries.
The main greenhouse gases are water vapor, carbon dioxide, and methane. Atmospheric concentrations of carbon dioxide and methane have increased by 31% and 149%, respectively, above pre-industrial levels since 1750. These levels are much higher than at any time in the past 650,000 years, the period for which reliable data have been extracted from Antarctic ice samples.
The burning of fossil fuels has produced about 75% of the increase in carbon dioxide from human activity over the past 20 years. Most of the rest is due to changes in land use, particularly deforestation. Paleoclimatologist William Ruddiman has argued that the human impact on the global climate began about 8,000 years ago with the beginning of deforestation to make land for agriculture.
The International Plant Protection Convention predicts an additional 2-11°F rise in average surface temperature over the 21st century. This increase will lead to worldwide sea level rise (estimated between 4 and 30 inches), and is expected to increase the intensity of extreme weather events and change the amount and pattern of precipitation. Other impacts of global warming include changes in agricultural yields, receding glaciers, lower ozone layer, ocean acidification, species extinction, and increased ranges of disease vectors.
These factors are likely to pose significant geopolitical and security challenges as countries around the world compete for water and other increasingly scarce natural resources. Population shifts are likely to occur worldwide as sea level rise threatens cities located in low-lying coastal areas. This may increase the potential for armed conflicts as national cohesion may be threatened by population loss or swelled migration from affected areas.
Although these scientific facts and predictions are shocking, there are reasons for hope. Paul Hawken, in his book Blessed Disorders: How the World’s Greatest Movement Came into Being and Why Nobody Saw It Coming, believes we are in the midst of the rise of world-changing activist groups, all “working toward environmental sustainability and social justice.”
This widely diverse global movement of many thousands of nonprofit and community-based organizations is neither ideological nor decentralized, but combines spontaneous and organic responses to the recognition that environmental problems are problems of social justice.
This was underlined by the awarding of the Nobel Peace Prize in 2007 to former Vice President Al Gore and the Intergovernmental Panel on Climate Change “for their efforts to build and disseminate greater knowledge about man-made climate change, and to lay the foundations for measures to counter such change.”
We have the knowledge, tools and ingenuity to tackle this most critical challenge facing humanity. It will require far-reaching vision, the political will to act, and the ability to rise above national self-interest and cooperate on a global scale.