Deforestation Has Driven Up Hottest Day Temperatures, Study Says
By Daisy Dunn
The average hottest day of the year in Europe, North America and Asia has been made significantly more intense as a result of deforestation since the start of the industrial revolution, a study finds.
The research considers the dual impact that deforestation has on the climate: first, that clearing forests releases CO2 into the atmosphere where it contributes to rising global temperatures; and second, the large impact it can have on physical processes in the local climate—which can have a net warming or cooling effect more widely.
The combined impact of deforestation has been so large in some areas that, until around 1980, it played a greater role in hottest day temperature rise than greenhouse gas emissions, the lead author told Carbon Brief.
The findings suggest that replanting trees—via afforestation or reforestation—could be a way of shielding against further increases in hottest day temperatures, the author added.
The new study, published in Nature Climate Change, estimates how deforestation from the start of the industrial era to recent times has affected temperatures on the hottest day of the year for a range of countries.
Deforestation is a key contributor to human-caused climate change. When forests are cleared or burnt, they release the carbon they store. Removing trees also diminishes an important carbon "sink" that takes up CO2 from the atmosphere.
Since 1990, around 129m hectares of forest—an area roughly the size of South Africa—have been chopped down by humans. Deforestation, along with other types of land use change, accounts for close to 11 percent of annual global CO2 emissions. From 1861-2000, deforestation accounted for 30 percent of CO2 emissions, according to the new research.
Deforestation can also affect temperatures through its effect on a range of different physical processes. These effects occur at local and regional scales, but can have global repercussions.
One such process is evapotranspiration, a term describing the exchange of water between the land and the atmosphere.
As part of this process, forests absorb water from the soil through their roots and later release it into the air as moisture, which has a cooling effect on the air above. When trees are cut down, this cooling effect disappears.
When these physical processes are considered alongside the impacts of carbon release, it is possible to deduce that deforestation has played a "significant" role in driving up hottest day temperatures, says lead author Dr. Quentin Lejeune. Lejeune is currently a research associate at Climate Analytics, a not-for-profit climate science and policy institute based in Berlin. He told Carbon Brief:
"During the industrial period, many areas over the mid-latitudes—especially in North America, the current Eastern Europe and Russia—experienced high rates of deforestation. We found that this led to significant local increases in daytime temperature during hot days."
For the study, the researchers used a group of climate models to "reconstruct" historical hottest day temperatures between 1861 and 2000.
Their simulations considered the role deforestation played in hottest day temperatures through both carbon release and its effect on physical processes. They also considered a range of other factors that can influence global temperatures, including greenhouse gas emissions, aerosols and volcanic eruptions.
The results show that, in regions where at least 15 percent of forest cover has been removed from pre-industrial times to today, deforestation accounts for one third of the increase in temperature of the average hottest day of the year. Lejeune said:
"Because deforestation occurred relatively early in the industrial period, we estimate that these processes were—for a long time—the biggest contributor to warming during hot days over these regions. [This effect was] superseded by the effect of increased greenhouse gas concentrations in the second part of the 20th century."
The map below shows the local effects of deforestation on hottest day temperatures in different parts of the world from present day (1981-2000), when compared to pre-industrial conditions.
On the charts, red is used to show a net increase in the temperature on the hottest day of the year, while blue shows a net decrease. Boxes are used to highlight the results for North America (left), Europe (middle) and Asia (right).
Lejeune et al. (2018)
Above: Local effects of deforestation on temperature change on the hottest day of the year from present day (1981-2000), when compared to pre-industrial conditions. Colour shows regional temperature increases (red) and decreases (blue). Boxes highlight the results for North America (left), Europe (middle) and Asia (right).
The results show that the effect of deforestation on hottest day temperatures was largest across North America and Europe, said Lejeune:
"Over the Central U.S., we estimate the daily maximum temperature during the hottest day of the year has increased by up to 1C due to these processes."
Both North America and Europe saw massive amounts of deforestation through the industrial revolution, the research notes. In the second half of the 19th century in the U.S., for example, an average of 34 square kilometers of forest was cleared every single day to make way for settlements and farming.
However, some regions that have recently experienced large amounts of forest loss, such as Brazil, experienced a net decrease in hottest day temperatures.
This could be down to how the removal of trees affects land albedo—or the proportion of sunlight that is reflected back towards space, Lejeune said.
Trees are generally dark in color and so do not reflect back a large proportion of sunlight. However, once they are removed, the bare surface that remains tends to be lighter and reflects back a larger proportion of sunlight. Therefore, deforestation can have a local net cooling effect in the short term.
In North America and Europe, deforested land is more likely to have been converted to urban spaces, which also tend to have a low albedo. As a result, the cooling effect of deforestation in these regions is likely to have been outweighed by warming impacts.
The research highlights the "considerable" impact that deforestation and other types of land use change can have on temperature rise, particularly on the local scale, said Lejeune:
"Decision makers who have to decide what the land should be used for—agriculture, biodiversity protection, reforestation to sequester carbon—should be aware that these decisions can have implications for the climate of the particular region that they live in."
The findings also suggest that restoring forest cover ("reforestation") and planting new forests ("afforestation") could help to shield against further increases in hottest day temperature, he added:
"Our results suggest that reforestation and afforestation could be effective at lowering regional temperatures, for these particular regions and this particular time of the year."
The new research is "useful" but relies on models that do not capture all of the effects of land use change on hottest day temperature increases, said Prof. Andrew Pitman, director of the Australian Research Council Centre of Excellence for Climate Extremes, who was not involved in the study. In 2012, Pitman was the lead author of a research paper finding that past deforestation and other land use change has caused a decrease in in extremely warm daytime temperatures over mid-latitude regions. He told Carbon Brief:
"The models they use—which are the only models they could have used – do not represent well the synoptic-scale processes like blocking and therefore the reliability of their results is unclear."
"Blocking" patterns are areas of high pressure that remain nearly stationary and therefore block the movement of other weather systems. Blocking patterns can stay in place for up to a week, leading to countries beneath them experiencing prolonged periods of hot weather, such as heatwaves.
In addition, the cooling effect of reforestation projects is likely only to have local benefits, Pitman added:
"The scale of reforestation in the next 50 years will be trivial in comparison [to historical deforestation]. I therefore doubt that reforestation would have a large impact at any reasonable scale. I do think it could have a major local impact."
Reposted with permission from our media associate Carbon Brief.
- Chemicals in Cosmetics Linked to Lung Damage in Children, New ... ›
- 33 Toxic Hair Straighteners Under International Recall Still Sold in US ›
EcoWatch Daily Newsletter
As the coronavirus has spread around the globe, so have the germs of misinformation and conspiracy theories about the new disease. Fake news about the virus is so prevalent that health professionals have started referring to it as an "infodemic."
- Doctors Aren't Just Fighting a Pandemic, but Also an 'Infodemic ... ›
- Trump Orders Hospitals to Stop Sending COVID-19 Data to CDC ... ›
- Facebook, Twitter Remove Trump Posts Sharing False COVID-19 Info ›
A new report shows the U.S. government bought more than $350 million in bonds issued by oil and gas companies and induced investors to loan the industry tens of billions more at artificially low rates since the coronavirus pandemic began, Bloomberg reported.
- Fed's Corporate Debt-Buying Could Mean Big Oil Bailout - EcoWatch ›
- Marathon Petroleum Takes Bailout Tax Breaks During Pandemic ... ›
By Karen Charman
When President Donald Trump visited California on September 14 and dismissed the state Secretary of Natural Resources Wade Crowfoot's plea to recognize the role of climate change in the midst of the Golden State's worst and most dangerous recorded fire season to date, he gaslighted the tens of millions of West Coast residents suffering through the ordeal.
Foxes Guarding the Henhouse<p>Before he assumed power, Trump attacked regulations as unnecessary barriers to freedom and economic prosperity. Since taking office, he has targeted anything enacted by the administration of his predecessor, Barack Obama, and taken steps to withdraw the U.S. from the Paris agreement, the international effort to combat climate change. He has also staffed heads of key agencies with climate deniers of various stripes, forced out career public servants and created a hostile work environment for those who don't profess loyalty to his deregulatory agenda.</p><p>Like Trump himself, some of his cabinet choices displayed an audacious penchant for <a href="https://www.nytimes.com/interactive/2020/09/27/us/donald-trump-taxes.html?action=click&module=Spotlight&pgtype=Homepage" target="_blank">self-dealing</a> and abusing their positions of authority. One example is Trump's first Environmental Protection Agency (EPA) Administrator, Scott Pruitt, who aggressively worked to overturn Obama's climate regulations, spent most of his time in <a href="https://www.washingtonpost.com/national/health-science/trump-epa-head-steps-down-after-wave-of-ethics-management-scandals/2018/07/05/39f4251a-6813-11e8-bea7-c8eb28bc52b1_story.html" target="_blank" rel="noopener noreferrer">private meetings</a> with fossil fuel and chemical company executives, sidelined career EPA staff and reconfigured independent scientific advisory boards to make them more supportive of the industries EPA is charged with regulating. Dubbed "<a href="https://www.latimes.com/politics/la-na-pol-pruitt-leaves-20180705-story.html" target="_blank" rel="noopener noreferrer">one of the most scandal-plagued Cabinet officials in U.S. history</a>," Pruitt resigned in disgrace after revelations about his multiple brazen abuses, including using the agency as his personal concierge service and piggy bank.</p><p>Pruitt's deputy, Andrew Wheeler, a <a href="https://www.cbsnews.com/news/andrew-wheeler-acting-epa-administrator-former-number-two-before-scott-pruitt-resignation/" target="_blank">former coal industry lobbyist</a> and longtime Republican Washington insider, took over and has continued Trump's deregulatory agenda apace.</p><p>At the Department of Interior (DOI), a sprawling agency that oversees 75 percent of the country's public federal lands and includes the U.S. Geological Survey, which is tasked with evaluating natural hazards that threaten life and the health of our ecosystems, Trump installed another flamboyant anti-environmentalist to head the agency. Like Pruitt, Trump's first Interior Secretary Ryan Zinke aggressively attacked environmental regulations, <a href="https://www.washingtonpost.com/news/energy-environment/wp/2017/05/07/epa-dismisses-half-of-its-scientific-advisers-on-key-board-citing-clean-break-with-obama-administration/" target="_blank">ditched more than 200 advisory panels</a>, and pushed to open up vast swaths of public land to oil and gas drilling. Described by one environmental group as "<a href="https://www.washingtonpost.com/national/health-science/interior-secretary-zinke-resigns-amid-investigations/2018/12/15/481f9104-0077-11e9-ad40-cdfd0e0dd65a_story.html" target="_blank" rel="noopener noreferrer">the most anti-conservation Interior secretary in our nation's history</a>," Zinke was forced out after numerous highly publicized conflict-of-interest scandals.</p><p>The DOI is now run by Zinke's deputy secretary, David Bernhardt, another longtime Republican Washington insider and former oil industry lobbyist who has also been the subject of <a href="https://slate.com/news-and-politics/2020/05/this-is-still-happening-david-bernhardt-trump-lincoln.html" target="_blank">several government ethics complaints</a> for various violations favoring polluting industries.</p><p>More recently, longtime climate change denier David Legates, a climatologist at the University of Delaware previously <a href="https://insideclimatenews.org/news/19032015/u-delaware-refuses-disclose-funding-sources-its-climate-contrarian" target="_blank">funded by fossil fuel interests</a>, was hired for a <a href="https://www.npr.org/2020/09/12/912301325/longtime-climate-science-denier-hired-at-noaa" target="_blank" rel="noopener noreferrer">top job</a> advancing weather modeling and prediction at the National Oceanic and Atmospheric Administration (NOAA). Legates has called for <a href="https://www.democracynow.org/2020/9/18/noaa_david_legates_climate_crisis" target="_blank" rel="noopener noreferrer">increasing carbon emissions</a>.</p><p>The Trump administration has done much more than stack government agencies with fossil fuel industry proponents. It has removed or diluted discussion of climate change from as many government platforms as it can and decimated independent scientific advisory boards that provide unbiased, fact-based information the government needs to enact policies that protect the public. It has also <a href="https://thehill.com/policy/energy-environment/482352-trump-budget-slashes-funding-for-epa-environmental-programs" target="_blank" rel="noopener noreferrer">slashed environmental agency staffing and budgets</a>.</p>
The Damage So Far<p>A September 17 <a href="https://rhg.com/research/the-rollback-of-us-climate-policy/" target="_blank">report</a> by the Rhodium Group calculates that 1.8 billion tons more greenhouse gases will be released over the next 15 years as a result of climate change rollbacks the Trump administration has achieved so far. These include repealing Obama's main climate policy, the Clean Power Plan, which was intended to reduce dirty emissions from power plants; increasing pollution from cars by rolling back fuel economy standards and challenging California's longtime authority to set stricter emissions standards; targeting controls on hydrofluorocarbons, powerful greenhouse gases used mainly in refrigerators and air conditioners that also destroy the Earth's protective ozone layer; and allowing unreported and unregulated emissions of methane, another potent greenhouse gas, by oil and gas companies.</p><p>Besides these measures, Trump is also trying to gut core environmental statutes like the Clean Air Act, the Clean Water Act, the National Environmental Policy Act and the Endangered Species Act, all of which were enacted to protect human health and preserve a livable world.</p><p>The Paris agreement aims to keep the rise in average global temperatures at less than 2 degrees Celsius above pre-industrial levels and hopefully cap it at 1.5 degrees C or lower. We are now at approximately 1.2 degrees C and counting.</p>
- Trump Admin Guts Endangered Species Act in the Midst of Climate ... ›
- Climate Change Purged From White House Website - EcoWatch ›
- California Burns Because of the Climate Crisis While Trump ... ›
By Jan Ellen Spiegel
It wasn't so long ago that the issue of climate change was poised to play a huge – possibly even a decisive – role in the 2020 election, especially in the race for control of the U.S. Senate. Many people supporting Democratic candidates saw a possible Democratic majority as a hedge against a potential Trump re-election … a way to plug the firehose spray of more than 100 environmental regulation rollbacks and new anti-climate initiatives by the administration over its first term.
Potential Climate Voters<p>In a September 1 memo on climate and the election, Andrew Baumann, vice president of the consultants Global Strategy Group, wrote: "Few issues have seen as dramatic a shift in public opinion as climate change has over the last few years. Only marriage equality and the recent shift in views around racial justice outpace the rapid growth in the salience of climate change as an issue."</p><p>Calling it a "winning political issue" the memo says: "First, it is clearly a motivator for both younger and Latinx voters. Second, it has the power to move swing voters, particularly center-right white women."</p><p>Baumann points to a finding that when a group of such women were asked generic ballot questions, Democrats trailed by nine percentage points. But when the question was revised as a choice between:</p><p>"A Democrat who supports taking strong government action to combat climate change.<br>A Republican who opposes taking strong government action to combat climate change."</p><p>… the result was a 29 percentage point shift, putting Democrats ahead by 20 percentage points among that same group.</p><p>"I think it is playing a role," says Senator Sheldon Whitehouse, D-RI, a longtime outspoken climate activist who is on the Senate Environment and Public Works Committee and also on the Senate Democrats' Special Committee on the Climate Crisis. If Democrats win back the Senate, he stands to play an even more pivotal climate role as part of the majority. He is not up for re-election this year.</p><p><span></span>"I think from the Democratic side it's playing a role in generating enthusiasm – particularly making younger voters feel that they have a real stake in this election. On the Republican side, I think things have moved enough that candidates can no longer get away with simply scoffing about climate change."</p>
Climate a Top Concern for Youths, Latinx<p>So who's still thinking climate? Mostly young voters – 18 to 25 or 29 and Latinx voters.</p><p>Climate and the environment are the top concern among young voters, just above racism and healthcare according to <a href="https://circle.tufts.edu/latest-research/poll-young-people-believe-they-can-lead-change-unprecedented-election-cycle" target="_blank" rel="noopener noreferrer">CIRCLE</a>, the Center for Information and Research on Civic Learning and Engagement at Tufts University, which focuses on the political life of young people in the U.S. For Latinx youth, it drops a bit but remains in the top three.</p><p>The issues young people care about have an impact on how they volunteer their time, says Kristian Lundberg, an associate researcher at CIRCLE. He says that's played out most notably through the Sunrise Movement, which focuses on climate change and the environment along with other key activist groups such as Black Lives Matter and March for Our Lives.</p><p>He points to polling this summer that showed that 83% of 18-to-29-year-olds felt they had the power to change things. "Young people feel much more empowerment than in 2016 and 2018," Lundberg says. "It's intentional these movements are carving out space for young people. It's an important strategy."</p><p>In positions of power in these organizations, young people have developed peer-to-peer outreach on activism. And Lundberg says young people have made the leap that connects activism to voting as a lever for change. "In the past in very close races, young people breaking heavily have provided the margin of victory," he says.</p><p>CIRCLE is highlighting 10 U.S. Senate races as ones in which young voters can be decisive. Several of them have notable climate or environmental components – most prominently the Colorado and Montana races.</p><p>The Republican incumbents in each state – Cory Gardner in Colorado and Steve Daines in Montana – are running against a popular Democratic governor – John Hickenlooper in Colorado, now out of office — and Steve Bullock, still the governor of Montana. Both governors have had to balance their state's fossil fuel economic interests with supporting climate change solutions.</p>
Tying Climate Change to the Economy<p>In August, Data for Progress, a progressive research think tank, released polling on climate change – including in the battleground Senate elections in Arizona, Iowa, Maine, and North Carolina – showing voters back a Senate candidate supporting strong climate action.</p><blockquote>Climate change as 'mobilizing issue … key persuasion issue.'<br></blockquote><p>It also showed that linking climate change to the economy may be key. That means talking about clean energy and jobs together, says Danielle Deiseroth, climate data analyst for <a href="https://circle.tufts.edu/latest-research/poll-young-people-believe-they-can-lead-change-unprecedented-election-cycle" target="_blank">Data for Progress</a>. She says that in addition to jobs, climate change issues include climate justice and economic equality – both of heightened interest because of fallout from western wildfires.</p><p>"Climate change, we've observed over the last year or so, is a key mobilizing issue and a key persuasion issue," she says. "Climate issues can only grow support for Democratic candidates.</p><p>"I think it's pretty naive to say climate is the key issue for voters. For a lot of voters it really exemplifies so many things that are wrong with the Trump presidency," Deiseroth says.</p><p>So a factor among others. Helpful, but pivotal only in narrow circumstances.</p><p>At the League of Conservations Voters, a progressive environmentalist organization putting a lot of money and effort into the 2020 races, Senior Director of Political Affairs Craig Auster says: "I'll push back that climate change doesn't matter or isn't registering."</p><p>"It's still showing up in several Senate races. It's been playing a role in almost all of them."</p><p>Candidates are still talking about it, he says, pointing to Colorado, Montana, Iowa, and other states where ads are addressing climate and environmental issues. That shows the candidates believe their opponent is vulnerable on the issue or they're strong on it, he says.</p><p>Like others, Auster calls climate a motivator.</p><p>"Climate change matters," he says. "We have proof point after proof point about what's happening, whether it's a hurricane, a superstorm, derechos in Iowa, or wildfires out west.</p><p>"Pre-COVID it was top tier for Democratic voters along with healthcare. If COVID didn't happen I think climate would be a big deal."</p>
- Green New Deal Champion Ed Markey Defeats Joe Kennedy III ... ›
- These Races Will Shape How U.S. Elections Affect Climate Progress ... ›
- Outdoor Brand Patagonia Wants You to 'Vote the A**holes Out ... ›