Climate change threatens world’s oldest, tallest trees

Approximately one-third of the world’s old growth forests were lost between 1900 and 2015.

Climate change is killing the world’s oldest and tallest trees and shortening both the lifespan and height of younger trees, according to a new study published in the journal Science.

Large and old trees are being lost to warmer temperatures, wildfires, development, logging, invasive insects, and deforestation, noted the study’s lead author Nate McDowell of the Pacific Northwest National Laboratory in Richland, WA.

Old growth forests absorb and store large amounts of carbon dioxide. They are also home to many rare and endangered species and strongholds of biodiversity. Their loss will therefore accelerate global warming and ecological destruction.

“Perhaps more concerning is that the trajectory of all these disturbances are generally increasing over time and are expected to continue increasing in the future,” McDowell said.

A tree physiologist who works with the US Department of Energy‘s Pacific Northwest National Laboratory, McDowell assembled a team of more than 20 scientists, who reviewed over 160 previous studies on the deaths of trees worldwide.

The team studied records of old growth forests between 1900 and 2015 and found that almost one-third of old growth forest was lost during this 115-year period.

They then combined these studies’ findings with satellite data and computer models to produce what is likely the most detailed report of how forests on Earth are changing.

In North America and Europe, where more forest data is available than in other parts of the world, they found that the mortality of trees over the last 40 years has doubled.

The rates of old growth forest decline vary in different parts of the world; however, the researchers warned that the effects of the loss will be felt worldwide.

Disasters over this past year, such as wildfires in Siberia, the Amazon and Australia, decimated the world’s old growth forests, as did deforestation and illegal logging in Brazil and Southeast Asia.

In addition to causing or aggravating many of these disasters, climate change is inhibiting forests’ ability to recover from catastrophic events.

While increases in atmospheric carbon dioxide can spur tree growth in some locations, that growth is nowhere near enough to compensate for the losses caused by climate change, explained Kristina Anderson-Teixiera, an ecologist who heads the ForestGEO Ecosystems and Climate Program at the Smithsonian Conservation Biology Institute and took part in the study.

“We as a human society are hitting these forests so rapidly with so many different changes that they can’t keep up,” she said.

Carbon capture is key to meeting climate goals

Large-scale underground storage of carbon dioxide could help thwart the worst effects of global warming.

Capturing and storing just 2,700 Gigatonnes (Gt) of carbon dioxide underground would make it possible for the world to keep global warming below the critical threshold of two degrees Celsius over pre-industrial levels by 2100.

That is the finding of a new study conducted by scientists at the Imperial College in London and published in the latest edition of the journal Energy and Environmental Science.

The current rate of carbon capture and storage, known as CCS, is on track to meet the goal of the Intergovernmental Panel on Climate Change (IPCC) to hold the line to less than two degrees warming over pre-industrial levels by century’s end.

Previously, scientists had overestimated the amount of carbon storage needed to meet the above goal, citing the need to sequester 10,000 Gt of carbon dioxide to hold the line on global warming.

Carbon capture works by trapping carbon dioxide in the location where it is emitted and storing it underground where it cannot be released into the atmosphere.

In order to meet the goal of holding the line on global temperature increase to prevent catastrophic climate change, the current rate at which carbon dioxide is being stored must be upheld without delays, the study warns. Research to identify additional underground locations where carbon dioxide can be stored must actively continue.

According to Christopher Zahasky of Imperial’s Department of Earth Science and Engineering, now at the University of Wisconsin-Madison, the world’s capacity to store carbon dioxide underground has increased 8.6 percent over the last 20 years.

If carbon capture is conducted at this rate alongside other methods of emission reductions, such as increased use of renewable forms of energy, more energy efficiency, and powering public transportation electrically, the world could meet the crucial IPCC target, something many doubted as being attainable.

“Nearly all IPCC pathways to limit warming to two degrees Celsius require tens of gigatons of CO2 stored per year by mid-century. However, until now, we didn’t know if these targets were achievable given historic data, or how these targets related to subsurface storage space requirements,” Zahasky said.

“We found that even the most ambitious scenarios are unlikely to need more than 2,700 Gt of CO2 storage resource globally, much less than the 10,000 Gt of storage resource that leading reports suggest is possible. Our study shows that if climate change targets are not met by 2100, it won’t be for a lack of carbon capture and storage space.”

Global warming causing more powerful hurricanes

The number of hurricanes are increasing and global warming is to blame, say scientists.

Hurricanes are getting stronger as the world gets warmer, according to a new analysis.

Studying how hurricanes have changed over decades is difficult. The technological tools scientists use to study them changes constantly, making comparisons from different time periods hard to correlate. While research has generally suggested that global warming would result in more powerful and erratic hurricanes, it has been difficult to document with any degree of scientific certainty. Until now, that is.

A new study of hurricanes published May 18, 2020 in the journal Proceedings of the National Academy of Sciences, covers a period of 39 years from 1979 to 2017. Looking at the entire four-decade span and normalizing the data, researchers found a clear trend: storms are getting stronger and major tropical cyclones are occurring more frequently.

The 39-year period of the study overlaps a period when climate change has dramatically accelerated, according to reports by the National Oceanic and Atmospheric Administration (NOAA). The earth’s temperature has increased each year in the past 39 years, including eight of the 10 warmest ever recorded. 2018 and 2019, too recent to be included in the study, were also the warmest on record.

“The main hurdle we have for finding trends is that the data are collected using the best technology at the time,” James Kossin, a NOAA scientist and University of Wisconsin-Madison professor, said in a statement. “Every year the data are a bit different than last year, each new satellite has new tools and captures data in different ways, so in the end we have a patchwork quilt of all the satellite data that have been woven together.”

To create a consistent record, researchers removed the edges from newer, sharper tropical cyclone images to fit an older standard: images where each pixel represents a 5 square mile area (8 sq/km), taken once every three hours. They also excluded newer satellite images of storms using angles not available in 1998. The remaining dataset includes roughly 225,000 similar-quality images of some 4,000 global tropical cyclones stretching back to the 1980s.

Using the images of tropical cyclones to estimate wind intensity, measured in kilotons, researchers found that the chances of a tropical cyclone becoming a hurricane (sustained winds of 74 mph/119 km/h or higher) have increased significantly over the past 40 years. In addition, the odds of major hurricanes (100-knot storms) have gone up by about 15%, with most of that increase occurring in the last 19 years of the 39-year study period.

Climate impact is evident in the seasons

Footprint of humanity’s climate impact is visible in seasonal patterns around the world.

Scientists have determined that people are responsible for global warming by looking at weather records. They also can dust for fingerprints (ecological footprints) in other places.

A new study led by Lawrence Livermore National Laboratory’s Ben Santer looked for prints in a new place: the seasonal cycle of temperatures. The perfect tool for analyzing this is the global temperature record satellites produce.

The satellites do not go back quite as far as weather-station records, but the dataset is now long enough to be useful for climate studies. Several groups maintain separate satellite temperature datasets.

A huge amount of work went into all the necessary processing to produce temperature maps. Therefore, the different datasets do not always line up perfectly with each other.

Santer’s study involved using the most recent two versions of three different datasets. Each one tracks different layers of the atmosphere.

One record covers the lower troposphere. The other one covers the middle troposphere that is a little higher.

By tracking the difference between the coldest months and warmest summer months, they were able to see interesting regional patterns. The team averaged together the Northern Hemisphere’s mid-latitude stripe and discovered a larger seasonal temperature swing than in the Southern Hemisphere. The reason for this is there is a much greater area of land.

Nevertheless, this seasonal cycle has also increased significantly since 1979. It is a result of summer temperatures in the atmosphere rising faster than winter temperatures.

 

Great Barrier Reef ‘close to collapse’ due to climate change

A new plan suggests that climate change has brought the Great Barrier Reef “close to collapse.”

A plan endorsed by Australian federal and state governments suggests that the current climate change path means that the Great Barrier Reef is heading toward a “collapse.” A “new and improved” Reef 2050 plan released on Friday attempts to acknowledge that climate change poses a huge threat to the reef.

“Coral bleaching is projected to increase in frequency … those coral reefs that survive are expected to be less biodiverse than in the past,” the plan says, recognizing that “holding the global temperature increase to 1.5°C or less is critical to ensure the survival of coral reefs”.

“Respected coral scientists have documented in peer-reviewed journals that most of the world’s coral reefs will not survive unless the global temperature increase is limited to 1.5 degrees Celsius above pre-industrial levels,” it continued.

WWF-Australia head of oceans Richard Leck claims that Australia’s emissions reductions are not in line with limiting warming to 2 degrees Celsius.

“It is simply not good enough for the revised plan to suggest the global community must work to limit warming when Australia is not doing its fair share,” he said.

Australian Marine Conservation Society’s reef campaign director Imogen Zethoven claims that increased climate change recognition must be followed by action, suggesting that bleaching events would happen less often under an average temperature increase of 1.6 degrees Celsius.

“The onset of twice-a-decade bleaching will then become the onset of annual bleaching and eventually [the entire reef] will be affected,” she said.

Whether or not Australia will be able to save the Great Barrier Reef in time is yet to be seen.

Global warming might cause insects to eat more crops, study says

Research suggests that global warming might push insects to eat more crops, which will increase crop losses.

A new study suggests that climate warming will increase crop losses for critical food grains due to the increased metabolic rate and population growth of insect pests.

“Climate change will have a negative impact on crops,” said Scott Merrill of the University of Vermont, co-author of the study. “We’re going to see increased pest pressure with climate change.”

The team found that just a 2-degree increase in global temperature averages will cause total crop losses of around 213 million tons for rice, wheat, and maize crops. These losses will stem from increased insect metabolism.

“When the temperature increases, the insects’ metabolism increases so they have to eat more,” Merrill said. “That’s not good for crops.”

However, the connection to population growth is more complicated. Since insects have optimal temperatures for population growth, losses will be highest in temperate regions and less severe in tropics.

“Temperate regions are not at that optimal temperature, so if the temperature increases there, populations will grow faster,” Merrill said. “But insects in the tropics are already close to their optimal temperature, so the populations will actually grow slower. It’s just too hot for them.”

Ultimately, farmers will have to find novel pest management methods, such as adding new crop rotations or boosting pesticide use. However, not all of these strategies will be available to every farmer.

“There are a lot of things richer countries can do to reduce the effect, by increasing pesticide use or expanding integrated pest management strategies,” Merrill said. “But poorer countries that rely on these crops as staple grains will have a harder time.”

The findings were published in Science.

Climate change could make Earth’s ecosystems unrecognizable

A new study suggests that changes in the Earth’s vegetation due to climate change could make some of its ecosystems unrecognizable.

A new study suggests that dramatic changes in the Earth’s vegetation due to climate change could render the planet’s ecosystems unrecognizable.

“We’re already starting to see warning signs of big changes in vegetation across Australia, with declines in the Mountain Ash forests in Victoria and the Pencil Pine forests in Tasmania that are occurring, in large part, due to climate change,” said Simon Haberle from the Australian National University (ANU) Department of Archaeology and Natural History.

“Widespread and rapid changes to ecosystems are likely to have major knock-on effects for nationally important ecosystem services such as biodiversity, carbon storage and recreation,” he added.

“The palaeoecological data that was used for this study can be viewed as natural experiments exploring the response of ecosystems to drivers of change over time scales that can’t be captured by instrumental or historical records,” said Janelle Stevenson, co-author on the paper.

ANU analyzed datasets based on ancient pollen records from numerous sites in Australia and across the Pacific and South East Asia.

“Pollen reflects the changes in landscape and vegetation cover, and the beauty of these ancient pollen records is that they allow us to see these changes over thousands to millions of years,” Stevenson said. “The parts of Earth that had the biggest temperature increases over the time period analysed also had the most substantial changes in vegetation.”

“Our study provides yet another wake-up call that we need to act now to move rapidly towards an emission-free global economy,” she concluded.

The findings were published in Science.

Cold climates contributed to Neanderthal extinction, study says

A new study suggests that climate change, and cold climates in particular, probably contributed to Neanderthal extinction.

A new study suggests that climate change likely played a bigger role in the extinction of Neanderthals than we thought. The effort was a collaboration between many American and European research institutions and created detailed new natural records from stalagmites that reveal changes in the European climate over 40,000 years ago.

In particular, many of the cold periods coincide with many of the periods with no archaeological Neanderthals artifacts, which suggests that climate changes impact the long-term survival of the species.

“The Neanderthals were the human species closest to ours and lived in Eurasia for some 350,000 years,” said Vasile Ersek, co-author of the study. “However, around 40,000 years ago — during the last Ice Age and shortly after the arrival of anatomically modern humans in Europe — they became extinct.”

“For many years we have wondered what could have caused their demise,” he added. “Were they pushed ‘over the edge’ by the arrival of modern humans, or were other factors involved? Our study suggests that climate change may have had an important role in the Neanderthal extinction.”

The team believes that modern humans were able to survive these cold periods due to better adaptation to the environment.

“The comparable timing of stadials and population changes seen in the archaeologic and genetic record suggests that millennial-scale hostile climate intervals may have been the pacesetter of multiple depopulation-repopulation cycles” Ersek said. “These cycles ultimately drew the demographic map of Europe’s Middle-Upper Paleolithic transition.”

The findings were published in the Proceedings of the National Academy of Sciences.

Scientists discover ‘ticking time bomb’ heated ocean under Arctic

An underwater ocean under the Arctic is a “ticking time bomb” that could spell danger in the future.

Scientists just discovered evidence of a massive “ticking time bomb” in the form of a heated ocean underneath the Arctic Ocean. The reservoir penetrates deep into the polar region and threatens to melt the ice frozen on top.

“We document a striking ocean warming in one of the main basins of the interior Arctic Ocean, the Canadian Basin,” said oceanographer Mary-Louise Timmermans from Yale University.

Timmermans and her team examined temperature data on the Canada Basin from the last 30 years. The findings revealed that the amount of heat in the warmest region of the water had doubled during the period of 1987 to 2017.

The basin is formed from mixed layers of ocean water, with the warmer, saltier water trapped beneath cold, fresh water flowing at the surface. Although this unique dynamic is not new, the rapid heating conditions of the water underneath are concerning.

“Presently this heat is trapped below the surface layer,” Timmermans said. “Should it be mixed up to the surface, there is enough heat to entirely melt the sea-ice pack that covers this region for most of the year.”

“That heat isn’t going to go away,” said oceanographer John Toole from the Woods Hole Oceanographic Institution. “Eventually … it’s going have to come up to the surface and it’s going to impact the ice.”

Although it’s not an immediate threat, it could severely impact Arctic ice, and as of now, the ramifications are unclear.

“It remains to be seen how continued sea ice losses will fundamentally change the water column structure and dynamics,” the authors wrote, although they note that excess heat “will give rise to enhanced upward heat fluxes year-round, creating compound effects on the system by slowing winter sea ice growth.”

“We’re seeing more and more open water as the sea ice retreats in the summertime,” Timmermans said. “The Sun is warming up the ocean directly, because it’s no longer covered by sea ice.”

The findings were published in Science Advances.

Corals in deeper waters are stressed too, study says

Contrary to popular belief, corals in deeper waters experience significant thermal stress from ocean warming.

A new study suggests that corals in deeper waters are exposed to episodic thermal stress. Researchers previously believed that corals at a depth of 30 to 150 meters were safer than their shallow-water counterparts. But although the intervals of thermal stress they experience are different than corals at the surface, they still feel the effects of ocean warming.

The team reached their conclusions using almost two decades of data sets that include sea-surface temperature, sea level, and temperature observations that range from the surface to deep in the mesophotic zone. Using their unique approach, they were able to measure and predict the thermal stress of coral reefs at many depths.

“We’re now adding the dimension of depth into the problem where before we were only skimming the surface of what temperature stress meant for corals,” said Travis Schramek, lead author of the study. “We see that the heat-induced stress penetrates all the way into the mesophotic zone during larger bleaching events.”

“A surprising outcome of the study is that the oceanic conditions along the dramatic reef walls that are the boundaries of Palau are very representative of the broader Western Pacific,” said Scripps oceanographer Eric Terrill, senior author of the study. “As a result, we had a surprising amount of success in predicting the vertical structure of the temperature fields that the coral communities would be exposed to, even during El Niño conditions.”

The new insights from the study can help researchers predict the temperature stress on deep corals. Not only that, they can shed light on how the effects contribute to our understanding of the reef system as a whole.

The findings were published in Geophysical Research Letters.