The average air temperature near the Earth’s surface rose approximately 1.33 degrees Fahrenheit during the last 100 years. The Intergovernmental Panel on Climate Change (IPCC) reports that “most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in greenhouse gas concentrations via the greenhouse effect.”
These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries.
The major greenhouse gases are water vapor, carbon dioxide and methane. The atmospheric concentrations of carbon dioxide and methane have increased by 31% and 149% respectively above pre-industrial levels since 1750. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from Antarctic ice cores.
Fossil fuel burning has produced about 75% of the increase in carbon dioxide from human activity over the past twenty years. Most of the rest is due to changes in land use, particularly deforestation. Paleoclimatologist William Ruddiman has argued that human influence on the global climate began around 8000 years ago with the start of forest clearing to provide land for agriculture.
The IPPC projects a further 2-11 degree Fahrenheit rise in average global surface temperature during the 21st century. This increase will cause a worldwide rise in sea level (estimated between 4 and 30 inches), and is expected to increase the intensity of extreme weather events and to change the amount and pattern of precipitation. Other effects of global warming include changes in agricultural yields, glacier retreat, reduction in the ozone layer, acidification of the oceans, species extinctions and increases in the ranges of disease vectors.
These factors are likely to pose significant geopolitical and security challenges as countries around the globe compete for water and other increasingly scarce natural resources. Worldwide shifts in population are likely to occur as rising sea levels threaten cities located on lower-lying coastal areas. This may increase the likelihood of armed conflicts as national cohesion may be threatened by loss of population or swelling migration from affected areas.
Although these scientific facts and predictions are daunting, there are reasons for hope. Paul Hawken, in his book Blessed Unrest: How the Largest Movement in the World Came into Being and Why No One Saw It Coming, believes that we are in the midst of a world-changing rise of activist groups, all “working toward ecological sustainability and social justice.”
This widely diverse, worldwide movement made up of many thousands of nonprofits and community organizations is neither ideological nor centralized, but a coalescence of spontaneous and organic responses to the recognition that environmental problems are social-justice problems.
This is underscored by the award 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 up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change.”
We have the knowledge and tools and ingenuity to address this most serious challenge facing humankind. It will require long-range vision, political will to act, and an ability to rise above national self-interest and cooperate on a global scale.