June's heat wave breaks or matches 3,215 temperature records across the United States.
July is the hottest month ever Recorded in the continental United States.
The 12-month period from July 2011 to June 2012 is the hottest in recorded U.S. history—until August 2011 to July 2012 surpasses it.
Former climate-change skeptic Richard A. Muller, cofounder of the Berkeley Earth Surface Project, throws in the towel: "Humans are almost entirely the cause."
A dolphin is spotted swimming in the Hudson River off Manhattan. It is later found dead, apparently of starvation.
After reaching record-high levels in 2011, the Mississippi River hits a record low, slowing barge traffic to a standstill.
Prices for corn and soybeans skyrocketas a result of the drought covering more than half the United States, the most widespread dry spell in a generation. Natural disaster is declared in more than 1,800 counties in 38 states, the largest such area in history.
Arctic sea ice reaches the lowest extent ever measured, 27,000 square miles less than the previous record, established in 2007.
The Millstone nuclear power plant in Waterford, Connecticut, has to be shut down because the waters of Long Island Sound are too warm to cool it.
The Nuclear Regulatory Commission halts nuclear reactor construction and operating licenses until it conducts a study of the effects of storing and disposing of spent nuclear fuel.
Warm ocean temperatures in the Northeast lead to a glut of lobster, driving down prices for lobstermen, although not necessarily for diners.
The Obama administration raises fuel-economy standards for cars and light trucks to 54.5 miles per gallon by model year 2025. By then, vehicles will need to be twice as fuel efficient as new cars on the road today.
While the number of frogs is declining, the number of known species is rapidly increasing. Scientists catalog the 7,000th known amphibian, the Amazonian glass frog.
A judge in Brazil stops construction of the enormous Belo Monte Dam, saying that indigenous people living in the 260 square miles that the dam would flood haven't been sufficiently consulted.
In Iowa, 40,000 shovelnose sturgeon die when water temperatures reach 97 degrees.
According to the Centers for Disease Control and Prevention, an outbreak of West Nile virus has infected 1,590 people in 2012 and is on track to be the worst in U.S. history.
For the second time in eight years, the U.S. District Court of Appeals in Washington, D.C., blocks the EPA's attempt to reduce air pollution from coal-fired power plants that crosses state lines. The Sierra Club estimates such a rule could prevent 34,000 premature deaths per year.
The Energy Department predicts a 23 percent increase this year in electricity produced from natural gas and a 12 percent decrease in electricity from coal. —Paul Rauber
Left column from top: iStockphoto/Suzifoo, iStockphoto/SteveByland;
Right column from top: iStockphoto/VisualCommunications, iStockphoto/Tsuji, iStockphoto/jangeltun