Restoring tree cover is now firmly established as a strategy for removing carbon from the atmosphere to help tackle climate change.
But there is an elephant in the room when it comes to estimating just how promising a climate solution it is in different locations. This is “albedo” – the fraction of the solar radiation that is reflected from the Earth’s surface.
In essence, brighter surfaces – such as a large snowy expanse or a grassland – will generally reflect a high proportion of sunlight back into space. Trees, meanwhile, tend to be darker coloured and absorb more sunlight, keeping it on Earth – usually in the form of excess heat.
Because restoring tree cover often involves replacing brighter land covers – such as grasslands – with darker ones – namely, trees – this can lead to some degree of global warming.
In some locations, this warming can partially or even completely outweigh the benefit of increased carbon uptake by the trees. Many know of this problem, but it has been difficult to quantify the impact of albedo in specific locations.
In our new study, published in Nature Communications, we map albedo change from restoring tree cover and show that carbon-only estimates of the global climate benefits of tree-planting may be 20-81% too high.
Our maps reveal that the climate benefits of tree-planting in savannahs in Africa and central Asia would be the most reduced by albedo. But we show that it is possible to find places that provide net-positive climate mitigation benefits in all biomes.
Tree cover affects albedo
It is getting harder to ignore albedo when planning projects to restore tree cover for climate mitigation.
For example, a recent study published in Science showed that albedo, among other factors, could substantially reduce the climate mitigation benefit of restoring tree cover.
However, despite its importance, albedo is often only given a brief mention as an important factor in research attempting to quantify the climate benefits of restoring tree cover. Its impact is frequently not accounted for – or only via coarse adjustments.
In some places, restoring tree cover modifies albedo enough to dwarf smaller changes in carbon, leading to an overall (net) increase in global warming. In other locations, the impact of albedo does not outweigh the carbon removal, contributing to an overall global cooling effect.
Understanding and quantifying these variations in albedo and carbon change is crucial to the success of a project that aims to restore tree cover for climate mitigation.
Yet there has been a lack of tools to provide this information. Our study sets out to change that.
Mapping albedo change
Our study provides the maps that quantify the absolute and relative changes in albedo anywhere on Earth where we might grow trees.
We first created a series of 24 maps that quantified how albedo would change if an area transitioned from one of four open land cover classes – such as grassland or croplands – to one of six different forest-cover classes, such as deciduous broadleaf or evergreen needleleaf forest. These are useful for individual projects that know their starting and end conditions.
However, to examine general global patterns, we used a data-driven approach to model the albedo change resulting from the “most likely” open-to-forest transition for each part of the world. We then combined that with a map of maximum potential carbon storage to map net climate impact in carbon dioxide equivalents.
In this map (below), red and orange shading indicates regions where restoring tree cover leads to net warming and blue indicates regions where restoring tree cover leads to net cooling.
The map shows that, in many places, increasing tree cover is likely to contribute to global warming. These include the dryland ecosystems of central Asia and the Sahel region of Africa, as well as northern reaches of North America, Europe and Asia.
However, all biomes had at least some climate-positive locations, indicating that the coarse exclusions used in the past have missed opportunities. Moreover, some locations experience little to no albedo change, such as in south-east Asia, central Africa and the Amazon.
This map makes it possible for people to determine the best places to restore tree cover to achieve climate mitigation, as well as evaluate different scenarios of where restoration of tree cover might happen.
For example, we examined three previously published global studies of large-scale increases in tree cover. We find that, after accounting for albedo, the global climate mitigation benefit of restoring tree cover may actually be 20-81% lower than expected from carbon-only estimates.
Notably, the study with the greatest deduction included large areas of tree-planting within the tundra and other locations where we predict very negative climate outcomes. We show that constraining this study’s tree-planting to only the more climate-positive areas – about a third of the total area (311m hectares instead of 889m hectares) – would lead to a 2.5-fold increase in mitigation potential.
This demonstrates the value of strategic project placement to maximise climate benefit, because it is possible to achieve more mitigation with less investment of space.
Forest restoration projects
Encouragingly, our study also finds that hundreds of thousands of on-the-ground tree-planting projects tend to be concentrated in places where the potential for carbon removal is high and albedo change is moderate.
One example is the moist tropical ecosystems in Brazil and Indonesia. Most of these on-the-ground projects can be found at Restor, a data-driven and community-based platform that aims to accelerate restoration and makes it possible for the first time to evaluate outcomes of the global restoration movement.
This suggests that ongoing or planned projects are concentrated in places that are good for achieving climate mitigation. However, the majority – around two-thirds – of these on-the-ground projects still face an albedo offset of at least 20%, indicating that most – if not all – projects should consider albedo change in their accounting.
None of this is to criticise projects that fall in places with negative climate outcomes. There are many wider reasons for restoring tree cover in a given landscape, beyond climate mitigation, including cleaner water, wildlife habitat, stabilised soils, sustainable livelihoods and cooler local temperatures.
However, for projects where the emphasis is on achieving climate mitigation, it is important to consider changes in albedo alongside changes in carbon removal, especially now that the tools are available to do so.
In general, climate accounting is not for the faint of heart. There are many factors such as albedo that can alter the total climate mitigation of natural climate solutions. However, we are in a critical time when pragmatic decisions need to be made now about which climate solutions to deploy and where.
Alongside our study, we have produced a dedicated web platform – called “naturebase” – to help policymakers, practitioners, communities and governments identify where, why and how to implement nature-based projects with the highest carbon mitigation.
This tool includes maps, data and case studies to show how different natural climate solutions – including restoration of tree cover – could benefit the climate across the world.
Policymakers and land managers are under growing pressure to make complex choices in line with global agreements. We hope that the science in our study and the tools in the naturebase platform will help enable smarter, more nature-positive decisions.
The post Guest post: Mapping where tree-planting has the greatest climate benefit appeared first on Carbon Brief.
Guest post: Mapping where tree-planting has the greatest climate benefit
Drought and heatwaves occurring together – known as “compound” events – have “surged” across the world since the early 2000s, a new study shows.
Compound drought and heat events (CDHEs) can have devastating effects, creating the ideal conditions for intense wildfires, such as Australia’s “Black Summer” of 2019-20 where bushfires burned 24m hectares and killed 33 people.
The research, published in Science Advances, finds that the increase in CDHEs is predominantly being driven by events that start with a heatwave.
The global area affected by such “heatwave-led” compound events has more than doubled between 1980-2001 and 2002-23, the study says.
The rapid increase in these events over the last 23 years cannot be explained solely by global warming, the authors note.
Since the late 1990s, feedbacks between the land and the atmosphere have become stronger, making heatwaves more likely to trigger drought conditions, they explain.
One of the study authors tells Carbon Brief that societies must pay greater attention to compound events, which can “cause severe impacts on ecosystems, agriculture and society”.
Compound events
CDHEs are extreme weather events where drought and heatwave conditions occur simultaneously – or shortly after each other – in the same region.
These events are often triggered by large-scale weather patterns, such as “blocking” highs, which can produce “prolonged” hot and dry conditions, according to the study.
Prof Sang-Wook Yeh is one of the study authors and a professor at the Ewha Womans University in South Korea. He tells Carbon Brief:
“When heatwaves and droughts occur together, the two hazards reinforce each other through land-atmosphere interactions. This amplifies surface heating and soil moisture deficits, making compound events more intense and damaging than single hazards.”
CDHEs can begin with either a heatwave or a drought.
The sequence of these extremes is important, the study says, as they have different drivers and impacts.
For example, in a CDHE where the heatwave was the precursor, increased direct sunshine causes more moisture loss from soils and plants, leading to a drought.
Conversely, in an event where the drought was the precursor, the lack of soil moisture means that less of the sun’s energy goes into evaporation and more goes into warming the Earth’s surface. This produces favourable conditions for heatwaves.
The study shows that the majority of CDHEs globally start out as a drought.
In recent years, there has been increasing focus on these events due to the devastating impact they have on agriculture, ecosystems and public health.
In Russia in the summer of 2010, a compound drought-heatwave event – and the associated wildfires – caused the death of nearly 55,000 people, the study notes.
The record-breaking Pacific north-west “heat dome” in 2021 triggered extreme drought conditions that caused “significant declines” in wheat yields, as well as in barley, canola and fruit production in British Columbia and Alberta, Canada, says the study.
Increasing events
To assess how CDHEs are changing, the researchers use daily reanalysis data to identify droughts and heatwaves events. (Reanalysis data combines past observations with climate models to create a historical climate record.) Then, using an algorithm, they analyse how these events overlap in both time and space.
The study covers the period from 1980 to 2023 and the world’s land surface, excluding polar regions where CDHEs are rare.
The research finds that the area of land affected by CDHEs has “increased substantially” since the early 2000s.
Heatwave-led events have been the main contributor to this increase, the study says, with their spatial extent rising 110% between 1980-2001 and 2002-23, compared to a 59% increase for drought-led events.
The map below shows the global distribution of CDHEs over 1980-2023. The charts show the percentage of the land surface affected by a heatwave-led CDHE (red) or a drought-led CDHE (yellow) in a given year (left) and relative increase in each CDHE type (right).
The study finds that CDHEs have occurred most frequently in northern South America, the southern US, eastern Europe, central Africa and south Asia.
Threshold passed
The authors explain that the increase in heatwave-led CDHEs is related to rising global temperatures, but that this does not tell the whole story.
In the earlier 22-year period of 1980-2001, the study finds that the spatial extent of heatwave-led CDHEs rises by 1.6% per 1C of global temperature rise. For the more-recent period of 2022-23, this increases “nearly eightfold” to 13.1%.
The change suggests that the rapid increase in the heatwave-led CDHEs occurred after the global average temperature “surpasse[d] a certain temperature threshold”, the paper says.
This threshold is an absolute global average temperature of 14.3C, the authors estimate (based on an 11-year average), which the world passed around the year 2000.
Investigating the recent surge in heatwave-leading CDHEs further, the researchers find a “regime shift” in land-atmosphere dynamics “toward a persistently intensified state after the late 1990s”.
In other words, the way that drier soils drive higher surface temperatures, and vice versa, is becoming stronger, resulting in more heatwave-led compound events.
Daily data
The research has some advantages over other previous studies, Yeh says. For instance, the new work uses daily estimations of CDHEs, compared to monthly data used in past research. This is “important for capturing the detailed occurrence” of these events, says Yeh.
He adds that another advantage of their study is that it distinguishes the sequence of droughts and heatwaves, which allows them to “better understand the differences” in the characteristics of CDHEs.
Dr Meryem Tanarhte is a climate scientist at the University Hassan II in Morocco, and Dr Ruth Cerezo Mota is a climatologist and a researcher at the National Autonomous University of Mexico. Both scientists, who were not involved in the study, agree that the daily estimations give a clearer picture of how CDHEs are changing.
Cerezo-Mota adds that another major contribution of the study is its global focus. She tells Carbon Brief that in some regions, such as Mexico and Africa, there is a lack of studies on CDHEs:
“Not because the events do not occur, but perhaps because [these regions] do not have all the data or the expertise to do so.”
However, she notes that the reanalysis data used by the study does have limitations with how it represents rainfall in some parts of the world.
Compound impacts
The study notes that if CDHEs continue to intensify – particularly events where heatwaves are the precursors – they could drive declining crop productivity, increased wildfire frequency and severe public health crises.
These impacts could be “much more rapid and severe as global warming continues”, Yeh tells Carbon Brief.
Tanarhte notes that these events can be forecasted up to 10 days ahead in many regions. Furthermore, she says, the strongest impacts can be prevented “through preparedness and adaptation”, including through “water management for agriculture, heatwave mitigation measures and wildfire mitigation”.
The study recommends reassessing current risk management strategies for these compound events. It also suggests incorporating the sequences of drought and heatwaves into compound event analysis frameworks “to enhance climate risk management”.
Cerezo-Mota says that it is clear that the world needs to be prepared for the increased occurrence of these events. She tells Carbon Brief:
“These [risk assessments and strategies] need to be carried out at the local level to understand the complexities of each region.”
The post Heatwaves driving recent ‘surge’ in compound drought and heat extremes appeared first on Carbon Brief.
Heatwaves driving recent ‘surge’ in compound drought and heat extremes
Greenhouse Gases
DeBriefed 6 March 2026: Iran energy crisis | China climate plan | Bristol’s ‘pioneering’ wind turbine
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Energy crisis
ENERGY SPIKE: US-Israeli attacks on Iran and subsequent counterattacks across the Middle East have sent energy prices “soaring”, according to Reuters. The newswire reported that the region “accounts for just under a third of global oil production and almost a fifth of gas”. The Guardian noted that shipping traffic through the strait of Hormuz, which normally ferries 20% of the world’s oil, “all but ground to a halt”. The Financial Times reported that attacks by Iran on Middle East energy facilities – notably in Qatar – triggered the “biggest rise in gas prices since Russia’s full-scale invasion of Ukraine”.
‘RISK’ AND ‘BENEFITS’: Bloomberg reported on increases in diesel prices in Europe and the US, speculating that rising fuel costs could be “a risk for president Donald Trump”. US gas producers are “poised to benefit from the big disruption in global supply”, according to CNBC. Indian government sources told the Economic Times that Russia is prepared to “fulfil India’s energy demands”. China Daily quoted experts who said “China’s energy security remains fundamentally unshaken”, thanks to “emergency stockpiles and a wide array of import channels”.
‘ESSENTIAL’ RENEWABLES: Energy analysts said governments should cut their fossil-fuel reliance by investing in renewables, “rather than just seeking non-Gulf oil and gas suppliers”, reported Climate Home News. This message was echoed by UK business secretary Peter Kyle, who said “doubling down on renewables” was “essential” amid “regional instability”, according to the Daily Telegraph.
China’s climate plan
PEAK COAL?: China has set out its next “five-year plan” at the annual “two sessions” meeting of the National People’s Congress, including its climate strategy out to 2030, according to the Hong Kong-based South China Morning Post. The plan called for China to cut its carbon emissions per unit of gross domestic product (GDP) by 17% from 2026 to 2030, which “may allow for continued increase in emissions given the rate of GDP growth”, reported Reuters. The newswire added that the plan also had targets to reach peak coal in the next five years and replace 30m tonnes per year of coal with renewables.
ACTIVE YET PRUDENT: Bloomberg described the new plan as “cautious”, stating that it “frustrat[es] hopes for tighter policy that would drive the nation to peak carbon emissions well before president Xi Jinping’s 2030 deadline”. Carbon Brief has just published an in-depth analysis of the plan. China Daily reported that the strategy “highlights measures to promote the climate targets of peaking carbon dioxide emissions before 2030”, which China said it would work towards “actively yet prudently”.
Around the world
- EU RULES: The European Commission has proposed new “made in Europe” rules to support domestic low-carbon industries, “against fierce competition from China”, reported Agence France-Presse. Carbon Brief examined what it means for climate efforts.
- RECORD HEAT: The US National Oceanic and Atmospheric Administration has said there is a 50-60% chance that the El Niño weather pattern could return this year, amplifying the effect of global warming and potentially driving temperatures to “record highs”, according to Euronews.
- FLAGSHIP FUND: The African Development Bank’s “flagship clean energy fund” plans to more than double its financing to $2.5bn for African renewables over the next two years, reported the Associated Press.
- NO WITHDRAWAL: Vanuatu has defied US efforts to force the Pacific-island nation to drop a UN draft resolution calling on the world to implement a landmark International Court of Justice (ICJ) ruling on climate, according to the Guardian.
98
The number of nations that submitted their national reports on tackling nature loss to the UN on time – just half of the 196 countries that are part of the UN biodiversity treaty – according to analysis by Carbon Brief.
Latest climate research
- Sea levels are already “much higher than assumed” in most assessments of the threat posed by sea-level rise, due to “inadequate” modelling assumptions | Nature
- Accelerating human-caused global warming could see the Paris Agreement’s 1.5C limit crossed before 2030 | Geophysical Research Letters covered by Carbon Brief
- Future “super El Niño events” could “significantly lower” solar power generation due to a reduction in solar irradiance in key regions, such as California and east China | Communications Earth & Environment
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
UK greenhouse gas emissions in 2025 fell to 54% below 1990 levels, the baseline year for its legally binding climate goals, according to new Carbon Brief analysis. Over the same period, data from the World Bank shows that the UK’s economy has expanded by 95%, meaning that emissions have been decoupling from growth.
Spotlight
Bristol’s ‘pioneering’ community wind turbine
Following the recent launch of the UK government’s local power plan, Carbon Brief visits one of the country’s community-energy success stories.
The Lawrence Weston housing estate is set apart from the main city of Bristol, wedged between the tree-lined grounds of a stately home and a sprawl of warehouses and waste incinerators. It is one of the most deprived areas in the city.
Yet, just across the M5 motorway stands a structure that has brought the spoils of the energy transition directly to this historically forgotten estate – a 4.2 megawatt (MW) wind turbine.
The turbine is owned by local charity Ambition Lawrence Weston and all the profits from its electricity sales – around £100,000 a year – go to the community. In the UK’s local power plan, it was singled out by energy secretary Ed Miliband as a “pioneering” project.
‘Sustainable income’
On a recent visit to the estate by Carbon Brief, Ambition Lawrence Weston’s development manager, Mark Pepper, rattled off the story behind the wind turbine.
I