NASA Earth Observatory, Jesse Allen and Robert Simmon/USGS
Bright blue melt ponds dot the surface of the Greenland Ice Sheet on June 21, 2013, in an image taken by the Landsat 8 satellite. These melt ponds form in depressions in the ice in the spring and summer when the sun's rays return to the Arctic.
John Hyde/Design Pics/Corbis
The effects of global warming are frequently projected decades into the future, but two recent reports -- one from theU.S. Global Change Research Program
and the otherfrom the U.N.
-- put into sharp focus visible consequences of our warming planet. An increase in temperature, extreme weather, loss of ice and rising sea level are just a few of changes we can measure right now. Let's take a look at some of the most concerning trends.BLOG: War Of The Words: Climate Change Or Global Warming?
Glaciers are shrinking worldwide and permafrost is thawing in high-latitude and high-elevation areas, reports this year's Fifth Assessment Report from the Intergovernmental Panel on Climate Change.BLOG: Dire Outlook For Climate Impacts, New Report Says
Only a few extinctions are attributed to climate change, reports the IPCC, but climate change that occurred much more slowly, over millions of years, caused major ecosystem shifts and species extinctions. Land and sea animals are changing their geographic ranges and migratory patterns due to climate change.NEWS: Climate Change: Why Haven't We Done More?
Sea level around the world has increased by about 8 inches since 1880, reports the 2014 National Climate Assessment, which projects a 1 to 4 foot rise by the end of the century.PHOTOS: Craziest Environmental Ideas (That Could Work)
Massimo Brega/The Lighthouse//Vi/Visuals Unlimited/Corbis
Excess CO2 is dissolving in the ocean and decreasing the pH of seawater. The ocean is about 30 percent more acidic than it was in pre-industrial times. More acidity in the oceans makes it harder for animals to form calcium carbonate shells and skeletons and erodes coral reefs.11 Health Threats from Climate Change
The probability of a Sandy-like storm deluging New York, New Jersey and other parts of the East Coast has nearly doubled compared to 1950, according to the American Meteorological Society. Even weaker storms will be more damaging now than they were 10 years ago because of rising sea levels. Superstorm Sandy cost the nation $65 billion, according to the 2014 National Climate Assessment, and 2012's Hurricane Isaac cost $2.3 billion.
The global sea level rises along with the temperature for two major reasons. For one, heat causes water to expand, which causes the existing water to take up more space and encroach on the coast. At the same time, ice at the poles and in glaciers melts and increases the amount of water in the oceans.PHOTOS: Melting Glaciers
Across the United States, heavy downpours are on the rise, especially in the Northeast and Midwest. Increases in extreme precipitation are expected for all U.S. regions, reports the 2014 National Climate Assessment.NEWS: Shrinking Greenland Glacier Smashes Speed Record
Ted Soqui/Ted Soqui Photography/Corbis
The most recent IPCC report states with "very high confidence" that current climate-related extremes like heat waves, droughts, floods, cyclones and wildfires are showing that countries around the world, at all development levels, are significantly unprepared. The American Meteorological Society estimates that approximately 35 percent of the extreme heat in the eastern United States between March and May 2012 resulted from human activities' effects on climate. The AMS warned that deadly heat waves will become four times more likely in the north-central and northeastern United States as the planet continues to warm.NASA: Global Warming Goes On
Late-spring warmth brings a stunning new color to the dazzling white palette that dominates Greenland in the wintertime. The warmth means Greenland's melt season has started, and sapphire-blue pools will soon dot the ice sheet as its upper layer of snow and ice transforms into water.
In 2012, a rare combination of weird weather, unusual warmth and forest-fire soot pushed the summer melt into overdrive, according to several recent studies. Nearly the entire surface of the Greenland Ice Sheet melted, even in the cold, dry regions where Greenland's elevation soars above 10,000 feet (3,048 meters).
But in 2013, the summer melt returned to normal, according to the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado. Almost half of the surface melted — ranking 14th in the 33 years since satellite tracking started in 1981.
Now, scientists are closely watching the 2014 summer thaw, to see if it will repeat 2012's impressive meltdown or return to the more mundane trend seen since 1981. So far, the signs point to an average year. [In Photos: Greenland's Melting Glaciers]
"We're not expecting anything exceptional for the next two weeks, but it's very difficult to look beyond that point," said Marco Tedesco, a Greenland melting expert at the City University of New York and a polar programs director for the National Science Foundation. "I think we will be able to make a good diagnosis by mid-July."
Some of the factors that led to a low surface melt in 2013 are still in play. The North Atlantic Oscillation, an atmospheric pressure pattern over the Atlantic Ocean, is still in a positive phase, as it was in 2013. The positive phase favors cooler conditions and summer snowfall across Greenland and warm, dry weather over Europe.
Also, meltwater has been slow to appear across the ice this year, Tedesco said.
Bright blue melt ponds dot the surface of the Greenland Ice Sheet on June 21, 2013, in an image taken by the Landsat 8 satellite. These melt ponds form in depressions in the ice in the spring and summer when the sun's rays return to the Arctic.NASA Earth Observatory, Jesse Allen and Robert Simmon/USGS
"Besides a peak that happened in mid-May over the south part of Greenland, it doesn't look like there has been considerable melting so far," Tedesco told Live Science. "And, of course, there was a lot of melting in May in 2012 and only a little melting in 2013."
Widespread early melting can jump-start a big summer thaw, because melting kicks off an albedo feedback mechanism, Tedesco said. Albedo measures how much of the sun's energy is reflected. Fresh snow is more reflective than old ice and water. Melting sets up a feedback loop: When the young snow melts and exposes older ice, the darker ice absorbs more sunlight (has a lower albedo), which leads to more melting. (Melting in the snowpack also lowers its reflectivity.)
Other factors can also lower albedo, such as soot from pollution and forest fires. This effect could have contributed to the high-elevation melt in 2012, a recent study suggested. And forest fires are already raging in California, Alaska and Siberia, upwind of the powerful atmospheric jets that travel eastward to Greenland.
But summer snowfall can bury soot, muting its sunlight-absorbing power, Tedesco said.
"I would love a way to anticipate what's going to happen, but all of these factors have a really complicated effect," Tedesco said.
One new way to monitor the melt will be through the NSIDC, which is planning to build a daily Greenland melt tracking website, the agency said May 26.
The Danish Arctic research institutions are also providing daily updates on Greenland's surface melting.