Our new scientific assessment of how humans are affecting the climate is nothing short of alarming, yet it does contain some encouraging news.
The second “Indicators of Global Climate Change” report, published in Earth System Science Data, provides an annual update on a set of metrics originally assessed by the Intergovernmental Panel on Climate Change (IPCC).
With the latest IPCC assessment report on climate science completed in 2021 and the next one not expected until at least 2027, there is a substantial gap to fill.
This is crucial at a time when human activity is changing the climate system at a rate and scale not experienced since records began.
For 2023, which smashed the record for the warmest year, our best estimate of the warming caused by human activity is 1.31C above pre-industrial levels.
This is the first year where this estimate has reached the 1.3C threshold. Our report also shows that human-caused warming has been increasing at a rate of 0.26C per decade.
This high rate of warming is caused by a combination of greenhouse gas emissions being close to an all-time high and a reduction in the cooling impacts of aerosols as society tackles deadly air pollution.
Yet, there is some positive news: greenhouse gas emissions have not yet risen beyond pre-pandemic levels and there is evidence that the rate of increase in CO2 emissions over the past decade has slowed compared to the 2000s.
Tracking climate change
We track and document how datasets and methods evolve between IPCC report cycles. The aim is to increase transparency and consistency from one cycle to the next, as well as filling the gap between reports.
This takes an international team of more than 50 scientists, including former IPCC authors and curators of global datasets.
The work builds a chain of evidence from emissions to temperature change, bringing around 20 global datasets together, to make a consistent estimate of human-caused warming based on the best-available current data and science.
The data and their changes are displayed on a dedicated Climate Change Tracker platform, shown below.
Greenhouse gas emissions
The starting point for updating the indicators is data on greenhouse gas (GHG) emissions. The most recent decade we have data for (2013-22) shows that average global GHG emissions were equivalent to 53bn tonnes of CO2 (GtCO2) per year.
Total GHG emissions remain ever so slightly below the pre-pandemic high set in 2019, as the chart below illustrates.
With emissions rebounding in the wake of the Covid-induced lockdowns around the world, it is too early to say whether GHG levels have already peaked. For example, both CO2 emissions from coal and gas and emissions of non-CO2 gases are rising. Emissions from oil are also increasing again, but remain below pre-pandemic levels.
These growing emissions have been offset by a small decline in land-use emissions.
With the high levels of ongoing emissions, GHGs have continued to build up in the atmosphere. These in turn affect the heat gained by the Earth system, which is increasing its effective radiative forcing (ERF).
ERF resulting from human activity rose to 2.79 watts per metre squared (W/m2) in 2023, compared to 2.72 W/m2 in 2019. However, last year’s ERF is lower than 2022’s (2.91 W/m2), mainly because of the increase in aerosols from wildfires in 2023, which had a cooling effect. In 2023, the increased aerosols from wildfires more than compensated for the ongoing fall in sulphur emissions from shipping and other sources. (See sections below for more detail.)
Warming impact
High GHG emission levels are also affecting the Earth’s energy balance, with observations showing an increase in the rate of heating on land and in oceans. Satellites and ocean buoys are tracking unprecedented flows of heat into the Earth’s oceans, ice caps, soils and atmosphere.
This rate of heat flow has doubled from the levels seen in the 1970s and 1980s to 0.96W/m2 measured over 2011 to 2023. This means nearly 1W/m2 of additional heat is flowing into every square metre of the Earth surface, 24 hours a day, 365 days per year.
Human-caused global warming has also increased by 0.1C in the four-year gap in tracking since the last IPCC report.
Remaining carbon budget
Our publication also reassesses the remaining carbon budget – the amount of CO2 that can be emitted while still keeping global warming below a certain level.
In 2020, the remaining carbon budget for a 50% likelihood of staying below 1.5C was around 500GtCO2, with an uncertainty range of 300-900GtCO2. At current emissions rates, that would be exhausted within around 12 years.
Since then, CO2 emissions and global warming have continued. At the start of this year, the same budget stood at 200GtCO2, with a range of 100-450GtCO2. This would be blown within less than five years at current rates.
The remaining carbon budget is also impacted by future non-CO2 emissions such as methane, as well as the cooling effects of aerosols such as sulphates. With non-CO2 emissions expected to contribute to warming going forward, the carbon budget also accounts for their predicted warming effect.
In this future scenario, we also assume methane and nitrous oxide emissions decline; if they do not, the carbon budget will be even smaller.
Record warmth in 2023
Last year saw a large increase in global temperatures, approaching 1.5C above pre-industrial levels in some datasets and reaching 1.43C in the average of four datasets used in the IPCC report.
Seeing 1.5C total warming during one year – or even more than one – does not mean that the Paris Agreement has been breached, nor does reaching or exceeding 1.5C warming in a particular month or location.
The Paris Agreement’s long-term temperature goal reflects global, human-caused, long-term temperature change that excludes short-term natural variability in the climate system. However, higher and rising annual temperatures clearly mean that we are heading in the wrong direction.
Our indicators show that, for the 2014-23 decade, observed global warming was 1.19C, of which 1.19C – that is, 100% – was caused by human emissions.
This is shown in the chart below, which compares the estimated human contribution to warming in individual years (grey) with assessments for 2023 (red), the trend in 2023 (blue) and the 2014-23 decadal average (green).
For the individual year of 2023, humans were responsible for 1.31C of the 1.43C that was recorded globally. This means that there was a substantial contribution from other causes to the record temperatures of 2023.
Contributing factors
The reasons for the record warm 2023 are still being investigated – for example, they could include shipping emission reductions (see below) as well as natural factors, such as the climate phenomenon El Niño.
Sometimes these factors are not easily distinguished as human or natural. For example, growing forest fires and their impact on emissions and the climate system.
Last year, Canada experienced its most severe fire season of the modern era, while there were also catastrophic fires in Hawaii, the Mediterranean, central Amazonia and central Chile.
Establishing how much of this biomass burning, the resulting emissions of aerosols and their effect on the climate is from natural wildfires is not easy.
For example, if the wildfires were caused by higher temperatures, themselves caused by human activity, this would be a climate feedback rather than from direct human activity.
This is an area where development of a consistent approach across datasets is needed. The same goes for methane, where emissions are primarily from fossil fuel production, agriculture and waste. Yet, emissions are also increasing from tropical wetlands under a warming climate.
There has been a lot of interest in how sulphur regulations from shipping led to a rapid fall in sulphur dioxide emissions in 2020 and possibly contributed to high global temperatures in 2023.
Our paper makes a preliminary investigation of its climate impact and we find that the global radiative forcing effect of the declining emissions would likely only have had a minor role in the high 2023 global temperatures.
We estimate that, globally, the cooling effect of the aerosols from the fires in Canada likely dominated any warming effect from shipping emission regulation changes.
Next steps
As 2024 unfolds, we hope that the indicators can shed further light on how human activity is shaping our climate at rates and levels not previously seen.
The aim is that they help lay the groundwork for the level of ambition needed for the latest national pledges under the Paris Agreement – the 2035 nationally determined contribution (NDC) commitments – where we expect countries to put more ambitious targets forward to the UN Framework Convention on Climate Change (UNFCCC) by 2025.
Perhaps our next update, which will be delivered to the Bonn negotiations in 2025, will begin to track a change in direction for the climate system that reflects a realisation of stronger and ambitious climate action for the longer-term.
The post Guest post: Tracking the unprecedented impact of humans on the climate appeared first on Carbon Brief.
Guest post: Tracking the unprecedented impact of humans on the climate
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