House Speaker Nancy Pelosi with Hutani's Jon Blumenauer at Spencer Glacier in AlaskaGlobal warming scenarios are generally forecasts of the conditions that will exist in the future. But on a recent trip to Alaska I was shocked to learn the extent of the impacts that have already taken place. These are not projections that may or may not come about in the future. They are here now, and Alaskans are trying to mitigate the damage.

Alaska is one of the most impacted areas on the planet by global warming. In the period between 1979-2007, Arctic ice lost 53% of its average thickness. The total area of Arctic ice lost over that period of time is over one million square miles.

Impacts are seen in many other areas. The average summer temperature in the Yukon River has increased ten degrees Fahrenheit over the past 25 years – a phenomenal increase in such a short period of time. The summer temperature is now warm enough to support a parasite that wiped out 45% of the recent salmon run in the Yukon River, killing the fish and making the rotting meat inedible.

Forests are dying off at alarming rates as warming occurs. Hundreds of thousands of acres are being killed as temperatures rise, leading to increases in forests fires. The Alaskan Boreal forests are potentially threatened with extinction.

Human populations are also threatened. Eighty-five percent of Alaska’s communities are located in coastal areas, which are increasingly threatened by erosion. Currently 184 communities need to be relocated, which will cost hundreds of millions of dollars. If this is the pricetag for the relatively few moves required in a state with less than 700,000 people, imagine the cost to relocate heavily populated communities located on coastlines in the continental U.S.

Despite this evidence right in our own backyard, many Americans still question whether global warming exists, and how much of it is due to human causes. I defer to the International Panel on Climate Change for this analysis. The IPCC consists of hundreds of scientists from dozens of countries, and it has concluded that human activity is undeniably linked to the rapid changes we are now seeing.

But others take a different approach. During our visit to Spencer Glacier (which, incidentally, has receded one mile in the past 50 years), I spoke to a park official. “Skeptics counter this evidence [of human-caused warming] with claims that the earth has gone through warming and cooling cycles for millions of years – and they’re right,” she said. “But humans have never lived through a period of global warming before. It ought to scare the heck out of everyone, because life as we know it is going to change dramatically – and it’s already started, as we see here every day. We can adapt, but it will be difficult and very costly. We should be doing everything possible to slow this change.”

The impacts of global warming are not decades away. As the residents of Alaska can attest, they have arrived. Those of us in the continental U.S. would do well to learn more about what is happening there and take action to mitigate the damage. The sooner we act, the less disruptive and costly it will be.