Tag: climate change

Abrupt climate change linked with ocean current shutdown

‘Rollercoaster’ temps prevailed as iceberg flotillas invaded North Atlantic

iceberg
Can Arctic icemelt shut down crucial ocean currents? @bberwyn photo.

Staff Report

By studying chemical tracers in seafloor sediments, scientists have been able to show that periods of abrupt climate change during the last ice age are somehow linked with dramatic changes in key ocean currents, especially the Atlantic meridional overturning circulation, which carries heat from the tropics to the northern latitudes.

Specifically, the study looked at series of abrupt climate changes that occurred between 60,000 and 25,000 years ago, ending as the last ice age peaked. A press release on the study describes it as an era when “temperatures in the Northern Hemisphere went on a rollercoaster ride, plummeting and then rising again every 1,500 years or so.”

“People have long supposed this link between overturning circulation and these abrupt climate events. This evidence implicates the ocean,” said L. Gene Henry, the lead author of the study and a graduate student at Columbia University’s Lamont-Doherty Earth Observatory. The findings, published in the journal Science, show for the first time that the ocean’s overturning circulation slowed during every one of those temperature plunges — at times almost stopping. Continue reading “Abrupt climate change linked with ocean current shutdown”

Reaching Paris climate goals would help polar bears survive

New research suggests that capping global warming below 2 degrees Celsius would lower chances of big population decline by preserving critical sea ice

 Eric Regehr, U.S. Fish and Wildlife Service
Can these mighty Arctic predators survive the era of human-caused global warming?  Photo courtesy Eric Regehr, U.S. Fish and Wildlife Service.

Staff Report

Now that the world has a clear target for limiting global warming, scientists say they show how how achieving the goal would protect at least some ecosystems and vulnerable species from impacts.

One newly updated study found that aggressively cutting greenhouse gas emissions would help ensure the survival of polar bears, listed as threatened because of Arctic sea ice declines. Polar bears depend on the ice as platforms for feeding around the biologically rich continental shelves of the Arctic Ocean. Continue reading “Reaching Paris climate goals would help polar bears survive”

Colorado River pulse flow released surge of greenhouse gases

New growth in delta could offset CO2 released from riverbed

Colorado River delta
The Colorado River Delta captured in a 2004 image from the International Space Station. Via NASA Earth Observatory.
Our special series on the Upper Colorado River is made possible with support from the Colorado River Water Conservation District. Contact Summit Voice for other sponsorship opportunities and click on the banner to visit the river district online.
Supported by the Colorado River District.

Staff Report

Human management of natural ecosystems always has unintended consequences, and the Colorado River is no example. After decades of intense dam building and diversions, the mighty river is a mere shadow of it former self, reduced to a trickle in some places and polluted by return flows in others. Along its entire length, ecosystems, including riparian zones and native fish, have suffered, with some of the biggest impacts in the Colorado River delta.

In an effort to restore at least some key reaches of the river, scientists and water managers have teamed up to try mimic some of the Colorado’s natural functions, with controlled releases of water to build up beaches. Those efforts culminated in early 2014 during an eight-week experiment that unleashed a mighty torrent of water from Morelos dam (on the border with Mexico and the USA).

The huge surge (130 million cubic metres) of water raised river levels down to the delta, which has been starved of water for decades. Scientists closely monitored how the release — and potential future releases — affect agricultural crops and natural plant and animal life of the lower delta.

But the pulse flow had another side effect. As the water washed over earth and rocks that had been dried out for many years, it dissolved carbon and sent a surge of greenhouse gases into the atmosphere. Continue reading “Colorado River pulse flow released surge of greenhouse gases”

Climate: Slower currents during last ice age helped oceans store more carbon

A new study shows how ocean currents play a huge role in the global carbon cycle. @bberwyn photo.
A new study shows how the speed of ocean currents play a huge role in the global carbon cycle. @bberwyn photo.

New study helps explain how carbon flux changes over time

Staff Report

The shells of tiny ocean organisms called foraminifera have once again given climate researchers huge clues about the long-term carbon cycle in the world’s oceans. The information helps show the buildup of heat-trapping greenhouse gases will affect the climate.

A pair of new studies led by University of Cambridge scientists show that cold oceans at the peak of the last ice age about 20,000 years ago, circulated much more slowly, enabling them to store more carbon for longer than modern oceans. Continue reading “Climate: Slower currents during last ice age helped oceans store more carbon”

Sunday set: Changing world

Global warming will irrevocably alter the face of the Earth

The more I report on climate change and the environment, the more I learn to cherish the landscapes that I see, because it’s really starting to sink in that humankind, during this Anthropocene Age, is fundamentally changing Earth’s ecosystems, altering the climate and impacting the landscape on levels seem almost inconceivable.

Take the Danube River (or most other major rivers, for that matter), where I spent a few hours Saturday afternoon swimming to cool of from a hot summer day in the city. While the water offered cool relief, I couldn’t stop thinking about a story I wrote a few years ago about scientists who discovered how, at times, there’s more plastic pollution than fish larvae in Europe’s second-biggest stream.

And watching sunset colors tinge the Ötscher, the highest peak peak in the eastermost reaches of the Alps, was a reminder that global warming is inexorably changing mountain ecosystems to the detriment not only of nature, but to ancient agricultural practices that are a culturally important part of life in the Alps. Continue reading “Sunday set: Changing world”

Bleaching risk on the rise for Great Barrier Reef corals

Global warming is likely to overwhelm corals'
Global warming is likely to overwhelm corals’ built-in thermal tolerance mechanisms within the next few decades, leading to more bleaching and mortality. Photo courtesy Dr. Peter Mumby.

Study identifies bleaching and mortality thresholds for imperiled coral reefs

Staff Report

The steady rise in ocean temperatures projected for the next few decades will put more and more corals at risk of bleaching, as the warm water simply overwhelms their thermal tolerance mechanisms.

Recent research along the Great Barrier Reef shows that corals have been able to survive past bleaching events because they were acclimated to warmer temperatures by being exposed to a pattern of gradually warming waters in the lead up to each episode. But global warming is likely to change that, the scientists said.

Before long, temperature increases of as little as 0.5 degrees Celsius may push many corals over the edge as the warm water causes them to expel the algae-like dinoflagellates that help keep them alive and give them their color.

Lead author Dr. Tracy Ainsworth from Coral CoE said  bleaching is like a marathon for corals.

“When corals are exposed to a pre-stress period in the weeks before bleaching, as temperatures start to climb, this acts like a practice run and prepares the coral. Corals that are exposed to this pattern are then less stressed and more tolerant when bleaching does occur,” Ainsworth said. Continue reading “Bleaching risk on the rise for Great Barrier Reef corals”

California tree deaths part of global wave of forest mortality

Climate change is wiping out forests on a staggering scale

forests dying because of global warming
Red and dead lodgepole pines in Colorado. @bberwyn photo.
A beetle-killed lodgepole pine branch in Summit County, Colorado.
A beetle-killed lodgepole pine branch in Summit County, Colorado. @bberwyn photo.

Staff Report

California’s multiyear drought killed even more trees than previously thought, the U.S. Forest Service announced this week. Aerial and ground surveys show that 26 million trees across six counties in Southern California died, in addition to the 40 million trees that died statewide from 2010 to October 2015. Four years of drought, high temperatures and an outbreak of tree-killing bark beetles all contributed the historic levels of tree die-off, the agency said.

The tree mortality in California is the latest crest in a wave of forest die-offs in the past few decades linked with global warming. In the Southwest, an outbreak of ips beetles after the 2002 drought killed 80 percent of the piñon pine forests in the Four Corners region.

Around the same time, pine beetles started spreading across northern Colorado, parts of Wyoming and North Dakota, ultimately killing millions of acres of forest. And just as the pine beetle infestation waned, a spruce beetle outbreak in southern Colorado started to spread. Since 1996, spruce beetles have killed trees across about 1.5 million acres of forest.

Huge swaths of Colorado aspen forests also died in the early 2000s in a mortality event linked with extreme heat, and forest researchers say hardwood forests in the northern U.S. are also at risk from global warming. Continue reading “California tree deaths part of global wave of forest mortality”