ABSTRACT
Continued emission of billions of tons will increase atmospheric concentrations of greenhouse gases. The increased concentrations are projected to rise Earth’s average temperature, effect the patterns and amounts of precipitation, reduce ice and snow cover, thaw permafrost, raise sea level and increase ocean acidity, increase the frequency, intensity, and duration of droughts, heat waves, hurricanes and cold spells, change ecosystem features, and increase threats to human health. These changes will impact our food supply, water resources, infrastructure, ecosystems, and our health. Hence, substantial and sustained reductions in greenhouse gas emissions are essential, and in association with the execution of adaptation plans, the risks of climate change can be limited. Projections of changes in the climate system are made using a chain of climate models: simple climate models, models of intermediate complexity, and comprehensive General Circulation models that include Earth System models.
