From the EUROPEAN COMMISSION JOINT RESEARCH CENTRE and the “Dr. Roger Pielke Sr. was right” department. I suspect a whole bunch of climate models that don’t take this into consideration, and think CO2 is the dominant climate driver, are going to need to be revised.
Land use change has warmed the Earth’s surface
Natural ecosystems play a crucial role in helping combat climate change, air pollution and soil erosion. A new study by a team of researchers from the Joint Research Centre, the European Commission’s science and knowledge service, sheds light on another, less well-known aspect of how these ecosystems, and forests in particular, can protect our planet against global warming.
The research team used satellite data to analyse changes in global vegetation cover from 2000 to 2015 and link these to changes in the surface energy balance. Modifying the vegetation cover alters the surface properties – such as the amount of heat dissipated by water evaporation and the level of radiation reflected back into space – which has a knock-on effect on local surface temperature. Their analysis reveals how recent land cover changes have ultimately made the planet warmer.
“We knew that forests have a role in regulating surface temperatures and that deforestation affects the climate, but this is the first global data-driven assessment that has enabled us to systematically map the biophysical mechanisms behind these processes”, explains Gregory Duveiller, lead author of the study.
The study also looked beyond deforestation, analysing changes between different types of vegetation, from evergreen forests to savannas, shrublands, grasslands, croplands and wetlands. However, they found that the removal of tropical evergreen forest for agricultural expansion is the vegetation cover transition most responsible for local increases in surface temperature.
From a greenhouse gas perspective, the cutting of forests might only affect the global climate in the mid-to-long term. However, the scientists point out that local communities living in areas where the trees are cut will immediately be exposed to rising temperatures.
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The study was published in Nature Communications and the datasets behind are fully described in Scientific Data.
The mark of vegetation change on Earth’s surface energy balance
Abstract
Changing vegetation cover alters the radiative and non-radiative properties of the surface. The result of competing biophysical processes on Earth’s surface energy balance varies spatially and seasonally, and can lead to warming or cooling depending on the specific vegetation change and background climate. Here we provide the first data-driven assessment of the potential effect on the full surface energy balance of multiple vegetation transitions at global scale. For this purpose we developed a novel methodology that is optimized to disentangle the effect of mixed vegetation cover on the surface climate. We show that perturbations in the surface energy balance generated by vegetation change from 2000 to 2015 have led to an average increase of 0.23 ± 0.03 °C in local surface temperature where those vegetation changes occurred. Vegetation transitions behind this warming effect mainly relate to agricultural expansion in the tropics, where surface brightening and consequent reduction of net radiation does not counter-balance the increase in temperature associated with reduction in transpiration. This assessment will help the evaluation of land-based climate change mitigation plans.
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Introduction
Our novel approach adopts the space-for-time logic to multi-scale remote sensing products to quantify the potential effect that a complete transition from one vegetation class to another would have on the individual components of the surface energy balance and on the resultant change in land surface temperature. This information is spatially and temporally explicit, enabling us to draw a comprehensive picture of the geographic and seasonal patterns of these potential changes. The resulting data set is freely available and fully described in an accompanying data description publication30. We use this global data set to quantify the total effect on the surface energy balance resulting from all vegetation changes that have occurred during the period 2000–2015, and then translate this effect into a change of 0.23 ± 0.03 °C over the concerned land.
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Discussion
This study makes the first global scale data-driven assessment of how different vegetation changes can influence the surface energy balance. Altogether, our results quantify these influences across different geographic regions and biomes, confirming the need to jointly assess both radiative and non-radiative processes in order to estimate the changes in surface climate induced by land cover change. In particular, this assessment shows that in ecosystems where vegetation growth is limited by water availability the climate impacts of a vegetation cover transition are dominated by changes in evapotranspiration, whereas in ecosystems where vegetation growth is limited by energy, such as boreal shrublands, the perturbation of the surface temperature is dominated by changes in the radiative and aerodynamic properties of those ecosystems. The origin of actual vegetation cover change in the recent past is divided along the same lines, with direct anthropogenic changes (such as agricultural intensification) occurring mostly where evaporation dominates, while changes within natural ecosystems have generally been confined to higher latitudes where radiative and aerodynamic effects prevail.
Our results show that vegetation cover change over the period 2000–2015 has produced on average a brighter but warmer land surface. This apparently contradictory signal is controlled by the three dominant transitions driven by agricultural expansion in mostly tropical regions (from evergreen broadleaf forests, shrublands or deciduous broadleaf forests to cropland, Fig. 5), which each lead to similar increases in albedo, and consequent reductions in absorbed radiation and turbulent energy fluxes. This perturbation of the surface energy balance ultimately produces a counter-intuitive warming of areas with higher albedo because of stronger plant-mediated constraints on evaporative cooling, in accordance with recent findings that prove the central role of non-radiative biophysical effects mediated by evapotranspiration18.
Full paper, open access: https://www.nature.com/articles/s41467-017-02810-8
Actually
I am not sure they got it right.
My results show it is cooling where they chopped the trees (e.g. Tandil, ARG)
and it is warming where they turned a desert into an oasis (e.g. Las Vegas, USA)..
Using Trees and Vegetation to Reduce Heat Islands
https://www.epa.gov/heat-islands/using-trees-and-vegetation-reduce-heat-islands
John
Your report gives the wrong impression that vegetation helps cool the world.
Obviously, looking at the shade a tree provides, yes it does cool the spot below.
However, overall vegetation traps heat. I believe the reaction at night when it converts the CO2 (to sugar) is exothermic? Anyway, e.g. note the development of the minimum T over the past 40 years in Tandil (ARG) where they chopped the trees.and compare it with that of Las Vegas (USA) , where they turned a desert into an oasis.
Here is a report of Pielke’s findings as originally published on NASA’s web site as it appeared on Science Direct https://www.sciencedaily.com/releases/2002/10/021002070639.htm
Landcover Changes May Rival Greenhouse Gases As Cause Of Climate Change
Date:
October 2, 2002
Source:
NASA/Goddard Space Flight Center
Summary:
While many scientists and policy makers have focused only on how heat-trapping gases like carbon dioxide are altering our global climate, a new NASA-funded study points to the importance of also including human-caused land-use changes as a major factor contributing to climate change.
Share:
FULL STORY
While many scientists and policy makers have focused only on how heat-trapping gases like carbon dioxide are altering our global climate, a new NASA-funded study points to the importance of also including human-caused land-use changes as a major factor contributing to climate change.
Land surface changes, like urban sprawl, deforestation and reforestation, and agricultural and irrigation practices strongly affect regional surface temperatures, precipitation and larger-scale atmospheric circulation. The study argues that human-caused land surface changes in places like North America, Europe, and southeast Asia, redistribute heat regionally and globally within the atmosphere and may actually have a greater impact on climate than that due to anthropogenic greenhouse gases combined.
The study also proposes a new method for comparing different human-influenced agents of climate change in terms of the redistribution of heat over land and in the atmosphere. Using a single unit of measurement may open the door to future work that more accurately represents human-caused climate change.
“Our work suggests that the impacts of human-caused landcover changes on climate are at least as important, and quite possibly more important than those of carbon dioxide,” said Roger Pielke, Sr., an atmospheric scientist at Colorado State University, Fort Collins, Colo., and lead author of the study. “Through landcover changes over the last 300 years, we may have already altered the climate more than would occur associated with the radiative effect of a doubling of carbon dioxide.” If carbon dioxide (CO2) emissions continue at current rates, atmospheric CO2 concentrations are expected to double by 2050. Land surface changes will also continue to occur.
Types of land surface strongly influence how the Sun’s energy is distributed back to the atmosphere. For example, if a rainforest is removed and replaced with crops, there is less transpiration, or evaporation of water from leaves. Less transpiration leads to warmer temperatures in that area. On the other hand, if farmland is irrigated, more water is transpired and also evaporated from moist soils, which cools and moistens the atmosphere, and can affect precipitation and cloudiness.
Similarly, forests may influence the climate in more complicated ways than previously thought. For example, in regions with heavy snowfall, reforestation or afforestation would cause the land to reflect less sunlight, and more heat would be absorbed, resulting in a net warming effect despite the removal of CO2 from the atmosphere through photosynthesis during the growing season. Further, reforestation could increase transpiration in an area, putting more water vapor in the air. Water vapor in the troposphere is the biggest contributor to greenhouse gas warming.
Local land surface changes can also influence the atmosphere in far-reaching ways, much like regional warming of tropical eastern and central Pacific Ocean waters known as El Niño. El Niño events create moist rising air, thunderstorms and cumulus clouds, which in turn alter atmospheric circulations that export heat, moisture, and energy to higher latitudes. Tropical land surface changes should be expected to play a greater role on global climate than El Niño, given that thunderstorms prefer to form over land, and the fact that the large area of tropical land-use changes far exceeds the relatively small area of water responsible for El Niño. Impacts of land use changes are harder to detect because they are permanent, as opposed to El Niño, which comes and goes.
Pielke Sr., and colleagues propose a new method for measuring the impacts of both greenhouse gases and landcover changes by using a formula that quantifies all the various anthropogenic climate change factors in terms of the amount of heat that is redistributed from one area to another. This heat redistribution is stated in terms of watts per meter squared, or the amount of heat associated with a square meter area. For example, if a flashlight generated heat of one watt that covers a square meter, then the heat energy emitted would be one watt per meter squared.
By using a measure based on the spatial redistribution of heat to quantify the different human influences on climate, including landcover changes and greenhouse gases, the researchers hope to achieve a more accurate portrayal of all of the anthropogenic influences on climate change in future research.
The paper was published in a recent issue of the Philosophical Transactions of the Royal Society of London. The research was funded by grants from NASA and the National Science Foundation.
Story Source:
Materials provided by NASA/Goddard Space Flight Center. Note: Content may be edited for style and length.
https://www.gsfc.nasa.gov/topstory/20020926landcover.html
And if you follow the link to the article shown above, this is what you would see for the last decade
“404 page not found”
TRY THIS http://www.gsfc.nasa.gov:80/topstory/20020926landcover.html and click the button
While atop an 18+ thousand foot mountain in Mexico, I observed a great deal of dirt embedded in the glacial ice of what was reported to me as a shrinking ice cap. I would imagine, via the albedo effect, the suspended dust is contributing to melting. I suspect that nearby volcanic activity would explain some of the particulates and I am also aware of negative impacts of dust from Arizona and New Mexico on the snowpack in Southern Colorado.
The author points to an increase in warming due to a reduction in the evaporative cooling effect of forest cover. Is there a further issue with an increase in atmospheric dust when forests are cleared for farmland that has been measured?
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