New study suggests climate is very sensitive to greenhouse gases
Although the rate of global warming has increased dramatically in the last few decades, a new study suggests that human activities have been driving climate change for the past 180 years. The findings suggest that global warming is not just a 20th century phenomenon, and that the climate system is, indeed, quite sensitive to the buildup of heat-trapping pollution.
The study was led by Nerilie Abram, of The Australian National University, who warming began during the early stages of the Industrial Revolution and started leaving a fingerprint in the Arctic and tropical oceans around the 1830s, much earlier than scientists had expected. Continue reading “Global warming started earlier than you think”→
New study suggests rapid meltdown during post-ice age warming
After taking a close look at rocks from West Antarctica’s dramatic Ellsworth Mountains, climate researchers say there’s a chance that ice sheets in the region could melt quickly as the planet warms, potentially causing sea level to rise by six to eight feet.
The new study, published in Nature Communications, took a close look at Antarctic climate change about 21,000 years ago during a period of warming after the coldest point of the most recent Ice Age. They found that the West Antarctic Ice Sheet reached a tipping point, after which it thinned relatively quickly, losing 400m of thickness in 3,000 years. Continue reading “What’s the tipping point for Antarctica’s ice sheets?”→
There was no letup to the global heatwave in July, according to the National Oceanic and Atmospheric Administration, which reported this week that the month ended up as the warmest ever recorded on planet Earth.
Federal climate trackers said it was the 15th month in a row with above average temps, making it the longest such streak in NOAA’s 137 years of record keeping. The global temperature for July has been above average for 40 years in a row, since 1976. July was also the 379th consecutive month with temperatures above the 20th century average. The last month with temperatures below the 20th century average was December 1984, at 0.09 degrees Celsius below average.
The combined average temperature over global land and ocean surfaces was 0.87 degrees Celsius above the 20th century average, besting the previous July record set in 2015 by 0.06 degrees Celsius. Across the world’s land areas, the average temperature was 1.10 degrees Celsius above the 20th century average. Continue reading “Climate: July breaks global temperature mark — again”→
‘Our study is for sea level what the now well-confirmed famous ‘hockey stick’ diagram was for global temperature’
The global rise of sea level may not be as dramatic or as easily visible as some other signs of global warming like melting glaciers, but it will be one of the most destructive and expensive long-term impacts. With a huge percentage of the world’s population living in coastal regions, society will need to take costly measures to protect people. In some cases, there will no option but to move entire communities away from the rising waters.
“Our study is for sea level what the now well-confirmed famous ‘hockey stick’ diagram was for global temperature,” said Stefan Rahmstorf, co-author of the paper on past sea-level rise and Co-Chair of PIK’s research domain Earth System Analysis. “We can confirm what earlier, more local sea-level data already suggested: during the past millennia sea-level has never risen nearly as fast as during the last century.”
The researchers said greenhouse gas emissions have caused at least half of the observed sea level rise in the 20th century, and possibly even all of it.
While the study didn’t break new ground in terms of projections, it’s important to be able to show with great certainty how much sea level will rise, Rahmstorf said.
“The new sea-level data confirm once again just how unusual the age of modern global warming due to our greenhouse gas emissions is – and they demonstrate that one of the most dangerous impacts of global warming, rising seas, is well underway.”
Barring any catastrophic climate feedback loops that could accelerate the meltdown of Arctic and Antarctic ice, the researchers said sea-levels worldwide will rise by 50 to 130 centimeters by the end of this century if greenhouse gas emissions are not reduced rapidly.
“With all the greenhouse-gases we already emitted, we cannot stop the seas from rising altogether, but we can substantially limit the rate of the rise by ending the use of fossil fuels,” said PIK’s Anders Levermann, who specializes in climate adaptation.
“We try to give coastal planners what they need for adaptation planning, be it building dikes, designing insurance schemes for floodings, or mapping long-term settlement retreat.”
Even if the world’s countries live up to the 2015 Paris climate agreement, sea level will rise 20 to 60 centimeters by 2100.
“This is quite a challenge, but less expensive than adaptation to unabated sea-level rise which in some regions is impossible”, Levermann adds. “If the world wants to avoid the greatest losses and damages, it now has to rapidly follow the path laid out by the UN climate summit in Paris.”
The likely future sea-level rise cannot be brought down to just one number, but is represented as a range, which at first sight might seem large.
“The range allows for a risk assessment,” said Ben Marzeion from the University of Bremen, Germany. “Coastal Planners need to know how a reasonable worst-case scenario as well as a well-founded best-case scenario look like to weigh chances and costs. The best available science is now converging towards a common uncertainty range of future sea-level rise. Curbing greenhouse gas emissions now gives us the chance to prevent sea level rise to accelerate further.”
Cool and stormy weather in the Arctic during July slowed the rate of sea ice loss to just below average for the month, making it less likely sea ice extent will dwindle to a record low, according to the latest update from the National Ice and Snow Data Center. But it all depends on conditions the next few months.
For the month, sea ice extent averaged 2.14 million square miles, the third-lowest for July since satellite records started in 1979. It was only the second month of 2016 that didn’t end with a record-low extent, according to the NSIDC. The sea ice extent in July was 73,000 square miles above the previous record low 637,000 square miles below the 1981 to 2010 long-term average. Through 2016, the rate of decline for the month of July is 28,070 square miles per year, about 7.3 percent per decade. Continue reading “Climate: Arctic sea ice melt slows slightly in July”→
Stored ocean heat will be released for centuries to come
Warming of at least 1.5 degrees Celsius over most of Earth’s land areas is probably already locked into the climate system — even if greenhouse gas concentrations were capped at today’s levels.
The new climate change warning came from UK scientists who, in a new study, differentiated between the warming over land areas and the average global temperature increases often used in discussions about efforts to limit emissions of CO2 and other greenhouse gases.