Knowledge News has a nice summary of the latest report from the Intergovernmental Panel on Climate Change (IPCC):

What IPCC Scientists Say Unequivocally It's Getting Warmer "Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level." "Eleven of the last twelve years (1995-2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850)." "The linear warming trend over the last 50 years . . . is nearly twice that for the last 100 years." Sea Levels Are Rising "Global average sea level rose at an average rate of 1.8 mm per year over 1961 to 2003. The rate was faster over 1993 to 2003, about 3.1 mm per year." "Observations since 1961 show that average temperature of the global ocean has increased to depths of at least 3000 m and that the ocean has been absorbing more than 80 percent of the heat added to the climate system. Such warming causes seawater to expand, contributing to sea level rise." "Mountain glaciers and snow cover have declined on average in both hemispheres. Widespread decreases in glaciers and ice caps have contributed to sea level rise." What IPCC Scientists Say Is "Very Likely" We're to Blame "Average Northern Hemisphere temperatures during the second half of the 20th century were . . . higher than during any other 50-year period in the last 500 years." "Global climate change of the past fifty years . . . is not due to known natural causes alone." "Most of the observed increase in globally averaged temperatures since the mid-20th century is . . . due to the observed increase in anthropogenic greenhouse gas concentrations." It Will Get Worse "Continued greenhouse gas emissions at or above current rates would cause further warming and induce many changes in the global climate system . . . larger than those observed during the 20th century." "Hot extremes, heat waves, and heavy precipitation events will continue to become more frequent." What IPCC Scientists Say Is "Likely" We're Changing the Weather "There has been significant anthropogenic warming over the past 50 years averaged over each continent except Antarctica." "Anthropogenic forcing . . . [has] contributed to changes in wind patterns, affecting extra-tropical storm tracks and temperature patterns in both hemispheres." "Future tropical cyclones (typhoons and hurricanes) will become more intense, with larger peak wind speeds and more heavy precipitation." --Steve Sampson