Map via NOAA.
That data comes from the National Oceanic and Atmospheric Administration's monthly "State of the Climate" recaps, which it does for the United States and the world at large. Each month, the reports outline the raw data: the XXth hottest month, YY degrees above the 20th century average. While the report includes broader trends in the warming, they tend to be a bit buried.
Which is why a report from The Economist last month made a bit of a splash: it suggested that global warming was actually happening more slowly than scientists expected. It didn't take long for reason to be offered. It wasn't because humans were producing less greenhouse gasses. Instead, blame volcanoes, eruptions of which emitted particles that helped diffuse sunlight in the stratosphere.
Global temperatures are never uniformly distributed, as the map above shows. If it's hot in Australia, that doesn't mean it will be here. According to the NOAA, March 2013 was tied for the tenth-hottest March in recorded history globally, matching March 2006. But after seeing its hottest year on record in 2012, temperatures during March in the United States were below the 20th century average for the month.
Map via NOAA.
The surprising cold the United States experienced was primarily due to an Arctic oscillation, a shift in pressure patterns that moves Arctic air south. The NOAA notes that the oscillation index provided "the most negative value on record for March."
Data resources: The Snow and Ice Data Center, Jim Pettit's Arctic ice graphs.
But there's some thinking that the Arctic ice melt played a role, too. ThinkProgress outlines the research in detail, but the key point: while "still not settled science," three recent studies suggest that dropping ice levels also lead to colder weather.
The level of ice in the Arctic always fluctuates. From its peak, usually in March, the amount of ice melts until it reaches its minimum extent, usually in September. Last year, the amount of ice at its lowest point was the smallest volume ever recorded.
Graph via Jim Pettit.
If scientists confirm a link between that melt and colder Springs, expect more Marches like the one we just experienced.
There are other implications to the ice melt, of course. Cargo ships can now pass through the fabled Northwest passage, cutting shipment times between Asia and Europe. Last year, a major general in the U.S. Northern Command suggested that North America would soon have a new coast: the shoreline on northern Canada.
Greenhouse gas emissions
Data resources: The EPA has a map tracking greenhouse gas emissions. The Department of Energy's Energy Information Administration tracks energy use and production.
Even as the United States produces more oil than it has in decades, the amount of carbon dioxide it creates — the most abundant type of greenhouse gas — has dropped. This is in part due to the slower economy since 2009, in part to the increased use of renewable sources, and in part due to the transition away from the use of highly polluting coal in power plants to cleaner natural gas — a transition spurred by low natural gas costs due, in part to fracking.