Sluggish Atlantic circulation could cause global temperatures to surge

Sluggish Atlantic circulation could cause global temperatures to surge

SOURCE: Nature DATE: July 18, 2018 SNIP: In a paper in Nature, Chen and Tung report that the system of ocean currents known as the Atlantic Meridional Overturning Circulation (AMOC) can explain changes in rates of global surface warming. Rather than the conventional picture of a vigorous AMOC associated with elevated surface temperatures in the Atlantic Ocean, the authors emphasize the role of the AMOC in taking heat from the surface and storing it in the deep ocean. Atmospheric concentrations of greenhouse gases are currently being increased at a rate that is unprecedented in millennia and most likely millions of years. As a result, the role that climate mechanisms might have had in the past might not be a good guide to their current or future role. The authors contend that half of the heat arising from ever-increasing greenhouse-gas concentrations is stored in the deep waters of the North Atlantic when the AMOC is increasing, thereby reducing overall global surface warming. The authors show that a cycle of increasing and then decreasing AMOC from the 1940s to the mid-1970s coincided with a period of global-warming slowdown; a quiescent period of weak AMOC from the mid-1970s to the late 1990s coincided with rapid global warming; and an increase in AMOC strength from the late 1990s to 2005 and a decrease thereafter coincided with the ‘hiatus’ in global warming. The AMOC is deemed “very likely” to weaken in the coming decades. Indeed, the Atlantic has seen muted rises in surface temperature relative to the global ocean over the past few decades. This relative lack of warming has been interpreted as a...
A building El Niño in 2018 signals more extreme weather for 2019

A building El Niño in 2018 signals more extreme weather for 2019

SOURCE: Grist DATE: May 22, 2018 SNIP: In case you couldn’t get enough extreme weather, the next 12 months or so could bring even more scorching temps, punishing droughts, and unstoppable wildfires. It’s still early, but odds are quickly rising that another El Niño — the periodic warming of the tropical Pacific Ocean — could be forming. The latest official outlook from NOAA and Columbia University gives better-than-even odds of El Niño materializing by the end of this year, which could lead to a cascade of dangerous weather around the globe in 2019. That’s a troubling development, especially when people worldwide are still suffering from the last El Niño, which ended two years ago. El Niño has amazingly far-reaching effects, spurring droughts in Africa and typhoons swirling toward China and Japan. It’s a normal, natural ocean phenomenon, but there’s emerging evidence that climate change is spurring more extreme El Niño-related events. On average though, El Niño boosts global temperatures and redistributes weather patterns worldwide in a pretty predictable way. Initial estimates show that, if the building El Niño actually arrives, 2019 would stand a good chance at knocking off 2016 as the warmest year on record. Images by Patrick Brown and NOAA’s National Weather...
Record Jump in 2014-2016 Temps Largest Since 1900

Record Jump in 2014-2016 Temps Largest Since 1900

SOURCE: University of Arizona DATE: January 24, 2018 SNIP: Global surface temperatures surged by a record amount from 2014 to 2016, boosting the total amount of warming since the start of the last century by more than 25 percent in just three years, according to new University of Arizona-led research. “Our paper is the first one to actually quantify this jump and identify the fundamental reason for this jump,” said lead author Jianjun Yin, a UA associate professor of geosciences. The Earth’s average surface temperature climbed about 1.6 degrees F (0.9 C) from 1900 to 2013. By analyzing global temperature records, Yin and his colleagues found that by the end of 2016, the global surface temperature had climbed an additional 0.43 degrees F (0.24 C). Co-author Jonathan Overpeck said, “As a climate scientist, it was just remarkable to think that the atmosphere of the planet could warm that much that fast.” The spike in warming from 2014 to 2016 coincided with extreme weather events worldwide, including heat waves, droughts, floods, extensive melting of polar ice and global coral...
The Window Is Closing to Avoid Dangerous Global Warming

The Window Is Closing to Avoid Dangerous Global Warming

SOURCE: Scientific American and San Diego Tribune (video) DATE: September 15, 2017 SNIP: Deadly climate change could threaten most of the world’s human population by the end of this century without efforts well beyond those captured in the Paris Agreement. That’s the finding of a pair of related reports released yesterday by an international group of climate science and policy luminaries who warned that the window is closing to avert dangerous warming. They say carbon dioxide might have to be removed from the atmosphere. Scientists Yangyang Xu and Veerabhadran Ramanathan found in a paper published in the Proceedings of the National Academy of Sciences (PNAS) that there already exists a 1 in 20 chance that the 2.2 trillion tons of carbon dioxide in the Earth’s atmosphere could cause an existential warming threat. This “fat tail” scenario would mean the world experiences “existential/unknown” warming by 2100 — defined in the report as more than 5 degrees Celsius above preindustrial levels. The report also found a 50 percent chance that temperatures would rise to 4 C under a business-as-usual scenario, a less extreme but still highly dangerous level. The long-term goal of the Paris accord was to maintain warming well below 2...
At Midway Point, 2017 Is 2nd-Hottest Year on Record

At Midway Point, 2017 Is 2nd-Hottest Year on Record

SOURCE: Climate Central DATE: July 18, 2017 SNIP: At the halfway point of the year, 2017 remains the second-hottest year to date — a surprise given the demise of the El Niño that helped boost temperatures to record levels last year. “Personally, I wasn’t expecting it to be as warm as it has been,” Ahira Sanchez-Lugo, a National Oceanic and Atmospheric Administration climate scientist, said in an email. “After the decline of the strong El Niño I was expecting the values to drop a bit and rank among the top five warmest years. This year has been extremely...