Tag: Dendrochronology

Tree-rings and shipwrecks offer clues on link between climate change and regional hurricane patterns

A NASA visualization of Hurricane Floyd approaching the Florida coast.
A NASA visualization of Hurricane Floyd approaching the Florida coast.

Study shows lull in tropical storms during cool era

Staff Report

Climate scientists and meteorologists have long been trying to determine how global warming will affect hurricanes, but with so many variables in play, it hasn’t been easy to make definitive conclusions.

A new analysis of tree rings and shipwreck records has now helped created a more detailed look at historic hurricane activity in the time before scientists were able to accurately count the tropical systems. The findings show there was a big drop in hurricanes between 1645 and 1715, during an era of reduced sunspot activity and generally cool temperatures in the northern hemisphere.

Learning that a lull in Caribbean hurricanes corresponded to a time when Earth received less solar energy will help researchers better understand the influence of large changes in radiation, including that from greenhouse gas emissions, on hurricane activity. Continue reading “Tree-rings and shipwrecks offer clues on link between climate change and regional hurricane patterns”

Climate: New tree-ring study suggests last winter’s California snowpack was the lowest in 500 years

A scant snowpack left California in a world of hurt. Photo courtesy NASA Earth Observatory.

‘We should be prepared for this type of snow drought to occur much more frequently because of rising temperatures …’

Staff Report

LINZ — A new tree ring study suggests this past winter’s snowpack in the Sierra Nevada may have been the lowest in 500 years — and there may be more of the same ahead, warned to researchers who analyzed the data.

“We should be prepared for this type of snow drought to occur much more frequently because of rising temperatures,” said Valerie Trouet, an associate professor of dendrochronology at the University of Arizona Laboratory of Tree-Ring Research. “Anthropogenic warming is making the drought more severe. Continue reading “Climate: New tree-ring study suggests last winter’s California snowpack was the lowest in 500 years”

Climate trends to trigger massive change in SW forests

A thermal emission sensor on NASA’s Terra satellite acquired this view of the Waldo Canyon, Colorado burn scar. 2012,  Vegetation-covered land is red in the false-color image, which includes both visible and infrared light. Patches of unburned forest are bright red, in contrast with areas where flecks of light brown indicate some burning. The darkest brown areas are the most severely burned.

Current conditions already reaching historic megadrought levels with widespread tree deaths expected in coming decades

By Summit Voice

FRISCO — Forests of the southwestern U.S. may be on the verge of dramatic changes in the coming decades, as a warming climate may squeeze many species of their narrow ecological niche.

New research shows that Southwest drought conditions in recent years are as intense as they were during the historic megadroughts of the 1200s and 1500s.

Southwestern forests grow best when total winter precipitation is high combined with a summer and fall that aren’t too hot and dry, but many climate models suggest the region will be warmer and drier. New Mexico just experienced its driest 24-month stretch on record.

If those conditions persist, it would likely result in widespread tree deaths and significant changes in the distribution of species on a regional landscape level, according to a new report published in the journal Nature Climate Change last week.

To measure the impacts of climate change, the scientists developed a stress index, factoring winter precipitation, late summer and fall temperatures, and late summer and fall precipitation into one number. Continue reading “Climate trends to trigger massive change in SW forests”

Study suggests Southwest fires driven by year-to-year weather cycles rather than long-term climate variations

A low-intensity ground fire burns through ponderosa pine during a prescribed fire in Grand Canyon National Park. PHOTO COURTESY NATIONAL PARK SERVICE.

New study offers more evidence that historical fire suppression is the main contributing factor in today’s big southwestern fires

By Summit Voice

SUMMIT COUNTY — A detailed analysis of historic fire-scar records and tree-ring data going back centuries offers more evidence that recent mega-fires in the Southwest are unprecedented and likely a result of widespread fire suppression.

While many of today’s southwestern forests haven’t seen a fire in more than 100 years, historical records show that, in the pre-suppression era, they rarely went as long as 40 or 50 years without a low-intensity ground fire.

To reach their conclusions, researchers at Southern Methodist University used a statistical model that encompassed 1,500 years of climate and fire patterns. They wanted to test if today’s dry, hot climate alone is causing the megafires that routinely destroy millions of acres of forest. Continue reading “Study suggests Southwest fires driven by year-to-year weather cycles rather than long-term climate variations”

Climate: How accurate are tree-ring records?

Tree rings generally offer a reliable way to track past climate changes, but a new study suggests the tree-ring record may not accurately reflect short-term cooling events. PHOTO VIA THE CREATIVE COMMONS.

Study suggests tree ring record may understate response to volcanic cooling

By Summit Voice

SUMMIT COUNTY — Scientists routinely use tree rings to study historic climate patterns and changes, but new research suggests that some of the data may be skewed because the reconstructions may underestimate the trees’ short-term response to intense volcanic eruptions.

In some cases, trees may not generate a new growth ring for a year or two following an eruption strong enough to cool the Earth’s atmosphere by several degrees. Such large temperature drops can shorten or even eliminate growing seasons, according to climate researchers, who compared tree-ring temperature reconstructions with model simulations of past temperature changes.

“The problem is that these trees are so close to the threshold for growth, that if the temperature drops just a couple of degrees, there is little or no growth and a loss of sensitivity to any further cooling,” said  Michael Mann, professor of meteorology and geosciences and director of the Penn State Earth System Science Center. Continue reading “Climate: How accurate are tree-ring records?”

Global warming causes growth spurt in some Arctic forests

New tree ring studies in Alaska help shed light on climate-change impacts to forests.

Tree-ring width and density increased dramatically about 100 years ago

By Summit Voice

SUMMIT COUNTY — Forests at the edge of Alaska’s tundra have put on a growth spurt in the past hundred years, and especially since about 1950, according to researchers with Columbia University’s LaMont-Doherty Earth Observatory.

The scientists  recently completed a detailed tree-ring study dating back to 1067. The results suggest that at least some forests may be adapting the rapidly warming climate in the Arctic. Global temperatures have climbed about 1.6 degrees since the 1950s, but some parts of northern latitudes have climbed about 4 to 5 degrees during that same span.

“For the moment, warmer temperatures are helping the trees along the tundra,” said study coauthor Kevin Anchukaitis, a tree-ring scientist at Lamont. “It’s a fairly wet, fairly cool, site overall, so those longer growing seasons allow the trees to grow more.” Continue reading “Global warming causes growth spurt in some Arctic forests”

CU team tracks Patagonian droughts and wildfires

Patagonian beech forests may become more fire-prone as ozone-depleting chemicals and greenhouse gases reinforce a cyclical climate pattern that leads to drought in the region.

Tree-ring study suggests the region could remain fire-prone for a century or more

By Summit Voice

SUMMIT COUNTY — A new study by CU Boulder researchers suggests that forests in Patagonia may become more fire-prone in the next 100 years, as a major climate oscillation in the southern hemisphere is reinforced and made more persistent by ozone-depleting chemicals and greenhouse gases.

The researchers used tree ring records dating back to 1506 to link past wildfire activity in the forests of Patagonia with the Southern Annular Mode, a climate cycle that creates low atmospheric pressure in the Antarctic that is tied to warmer and drier conditions in southern South America.

The tree rings showed that, when SAM was in its positive phase, there were widespread fires in both dry woodlands and rainforests in Patagonia, a region that straddles Argentina and Chile, said CU-Boulder Research Associate Andres Holz, lead study author. Continue reading “CU team tracks Patagonian droughts and wildfires”