Maine’s unusually warm winter may not be an anomaly, but part of a larger global warming trend. According to British researchers, the rise in temperatures around the world in the past century were larger and more widespread than any other global climate shift in the past 1,200 years.

No wonder the Pentagon, insurance companies and many countries are worried about – and planning for – the consequences of climate change. Ignoring this global issue, as the president did again in his recent State of the Union address, is irresponsible.

By analyzing temperature records, which go back only 150 years, and fossils, tree rings and ice cores for older data, scientists at the University of East Anglia found that temperatures, averaged across the globe, increased about 1 degree above normal and 2 degrees above the average in the late 1800s. Although the increase is small, it is more rapid that past changes and it is unusual for such a temperature swing to occur worldwide. Other drastic swings, such as the Little Ice Age, which froze the Northern Europe from 1580 to 1850, were more regional.

The increase has been even greater in recent years, with all of the 10 warmest years on record occurring since the mid-1990s. Last year was the warmest year on record, surpassing 1998, according to NASA.

Worse, the scientists warn, warming begets more warming. For example, melting sea ice perpetuates warming because open water absorbs more heat than ice or snow.

Sen. Susan Collins has seen melting sea ice and other evidence of climate change first hand in both the Arctic and Antarctica. On a recent trip to Antarctica, she was consistently told by scientist that putting a cap on greenhouse gas emissions was the most important thing Congress could do to slow the warming.

Congressional efforts to pass such a cap have repeatedly failed. Instead, states, regions and cities have passed their own caps. A national policy is preferred because those policies tend to produce better enforcement and they reduce the chance of industries merely moving across state borders or states making gains at the expense of pollution levels in other states.

An aggressive national policy is the only responsible response to a threat that becomes more apparent year by year.