As a result, glacier and ice-sheet melting, sea-ice retreat, coastal erosion and sea level rise could continue even if it doesn't feel warmer in Chicago.
A new synthesis of past Arctic climates lays out for the first time the pervasive nature of Arctic climate amplification. The U.S. Geological Survey led this new synthesis of published science literature using a team of climate scientists from academia and government. The U.S. Climate Change Science Program commissioned the report, which has contributions from 37 scientists from the United States, Germany, Canada, the United Kingdom and Denmark.
Chicago residents are hoping for some global warming. Photo: ghostwheelie
The new report makes several conclusions about the Arctic:
* Taken together, the size and speed of the summer sea-ice loss over the last few decades is highly unusual compared to events from previous thousands of years, especially considering that changes in Earth's orbit over this time have made sea-ice melting less, not more, likely.
* Sustained warming, more than approximately 4° to 13°F above average 20th century values, is termed 'likely to be sufficient' to cause the nearly complete, eventual disappearance of the Greenland ice sheet, which could raise sea level by several meters in the worst case scenario.
* The current rate of human-influenced Arctic warming is comparable to peak natural rates documented by reconstructions of past climates. However, some projections of future human-induced change exceed documented natural variability.
The past tells us that when thresholds in the climate system are crossed, climate change can be very large and very fast. We should not rule out that human induced climate change could trigger such events in the future.
"By integrating research on the past 65 million years of climate change in the entire circum-Arctic, we have a better understanding on how climate change affects the Arctic and how those effects may impact the whole globe," said USGS Director Mark Myers. "This report provides the first comprehensive analysis of the real data we have on past climate conditions in the Arctic, with measurements from ice cores, sediments and other Earth materials that record temperature and other conditions."
View the full report - Synthesis and Assessment Product 1.2: Past Climate Variability and Change in the Arctic and at High Latitudes.