An international examination of last year's weather concluded that 2012 was a good example of how long-term warming is overriding natural weather variability.
That doesn't mean natural variability doesn't exist and doesn't exert a powerful infuence. The flash drought that devastated the Central Plains last year was believed to be mostly a result of natural variability, federal researchers have said.
However, the fingerprints of climate change could be found in many places in 2012.
It was one of the 10 warmest years on record, according to the report. That wasn't an easy feat, given that an Earth-warming El Niño climate pattern was absent.
One of the many important regions where long-term trends are overriding variability is in the far north.
The sensitive region known as the Arctic is warming at about twice the rate of the lower latitudes. Arctic sea ice shrank seasonally to its smallest amount since observations began with the launching of satellites.
Records are being broken so consistently in the Arctic that it has become the new normal, according to one researcher.
Changes in the Arctic are no exotic issue. The Arctic exerts significant influence on weather in the Northern Hemisphere, including Nebraska and Iowa.
About 380 scientists from 52 countries participated in the peer-reviewed 2012 State of the Climate report.
For more information, visit www.climate.gov