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Analysis: Which countries are historically responsible for climate change?
Historical responsibility for climate change is at the heart of debates over climate justice.
History matters because the cumulative amount of carbon dioxide (CO2) emitted since the start of the industrial revolution is closely tied to the 1.2C of warming that has already occurred.
In total, humans have pumped around 2,500bn tonnes of CO2 (GtCO2) into the atmosphere since 1850, leaving less than 500GtCO2 of remaining carbon budget to stay below 1.5C of warming.
This means that, by the end of 2021, the world will collectively have burned through 86% of the carbon budget for a 50-50 probability of staying below 1.5C, or 89% of the budget for a two-thirds likelihood.
In this article, Carbon Brief looks at national responsibility for historical CO2 emissions from 1850-2021, updating analysis published in 2019.
For the first time, the analysis includes CO2 emissions from land use and forestry, in addition to those from fossil fuels, which significantly alters the top 10.
In first place on the rankings, the US has released more than 509GtCO2 since 1850 and is responsible for the largest share of historical emissions, Carbon Brief analysis shows, with some 20% of the global total.
Video shows, by ranked nation, cumulative CO2 emissions from fossil fuels, land use and forestry, 1850-2021 (million tonnes). Bottom right, remaining carbon budget to limit global warming at 1.5C (50-50 chance). Animation by Tom Prater for Carbon Brief.China is a relatively distant second, with 11%, followed by Russia (7%), Brazil (5%) and Indonesia (4%). The latter pair are among the top 10 largest historical emitters, due to CO2 from their land.
Meanwhile, large post-colonial European nations, such as Germany and the UK, account for 4% and 3% of the global total, respectively, not including overseas emissions under colonial rule.
These national totals are based on territorial CO2 emissions, reflecting where the emissions take place…
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Cooling effect of clouds ‘underestimated’ by climate models, says new study
Clouds could have a greater cooling effect on the planet than climate models currently suggest, according to new research.
The paper, published in Nature Climate Change, aims to correct a “long-standing” and “unaddressed” problem in climate modelling – namely, that existing models simulate too much rainfall from clouds and, therefore, underestimate their lifespan and cooling effect.
The authors have updated an existing climate model with a more realistic simulation of rainfall from “warm” clouds – those that contain water only, rather than a combination of water and ice. They find that this update makes the “cloud-lifetime feedback” – a process in which warmer temperatures increase the lifespan of clouds – almost three times bigger.
The authors note that the newest generation of global climate models – the sixth Coupled Model Intercomparison Project (CMIP6) – predicts faster future warming than its predecessors. This is largely because the new models simulate a smaller cooling effect from clouds.
However, the lead author of the study tells Carbon Brief that fixing the “problem” in rainfall simulations “reduces the amount of warming predicted by the model, by about the same amount as the warming increase between CMIP5 and CMIP6”.
Due to this, he says that the key takeaway from the study is to “take the extra warming in CMIP6 with a grain of salt until some of the other known cloud problems are also fixed in the models”.
Cooling clouds
The impact of clouds on global temperature is a complex area of research that scientists have been working on for decades.
In a Carbon Brief guest post published in 2018, Prof Ellie Highwood – professor of climate physics in the Department of Meteorology at the University of Reading – explains how clouds can affect global temperatures:
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Explainer: Will global warming ‘stop’ as soon as net-zero emissions are reached?
Media reports frequently claim that the world is facing “committed warming” in the future as a result of past emissions, meaning higher temperatures are “locked in”, “in the pipeline” or “inevitable”, regardless of the choices society takes today.
The best available evidence shows that, on the contrary, warming is likely to more or less stop once carbon dioxide (CO2) emissions reach zero, meaning humans have the power to choose their climate future.
When scientists have pointed this out recently, it has been reported as a new scientific finding. However, the scientific community has recognised that zero CO2 emissions likely implied flat future temperatures since at least 2008. The Intergovernmental Panel on Climate Change (IPCC) 2018 special report on 1.5C also included a specific focus on zero-emissions scenarios with similar findings.
Much of the confusion around committed warming stems from mixing up two different concepts: a world where CO2 levels in the atmosphere remain at current levels; and a world where emissions reach net-zero and concentrations begin to fall.
Even in a world of zero CO2 emissions, however, there are large remaining uncertainties associated with what happens to non-CO2 greenhouse gases (GHGs), such as methane and nitrous oxide, emissions of sulphate aerosols that cool the planet and longer-term feedback processes and natural variability in the climate system.
Moreover, temperatures are expected to remain steady rather than dropping for a few centuries after emissions reach zero, meaning that the climate change that has already occurred will be difficult to reverse in the absence of large-scale net negative emissions.
Constant concentrations vs zero emissions
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Guest post: Why avoiding climate change ‘maladaptation’ is vital
With the delayed UN climate talks coming up this year, COP26 president Alok Sharma recently launched a “Race to Resilience” to underscore the urgency of adapting to climate change.
However, in our new study – published in the journal World Development – we come to the unsettling conclusion that many adaptation projects can make people more, rather than less, vulnerable to climate change. This is known as “maladaptation”.
Academics and practitioners have spent many years promoting the idea that adaptation can reinforce sustainable development (pdf) and even offer a way to rethink development in light of the changing climate. So, is adaptation at an impasse?
No. In fact, we argue that adaptation is needed more than ever, but that it should be rethought.
Over the past decade, in the justified rush to provide assistance in the face of climate change impacts across the globe, many existing development aid institutions and approaches have been quickly re-purposed for the provision of “adaptation aid”.
But our analysis suggests that the timescales, participants and ultimate purpose of adaptation are often confused – resulting in well-intentioned, but misguided, investments that are backfiring to make climate change worse for many people.
The reality is that it is very difficult to give easy blueprints for “successful adaptation” – or how to measure it. This is because adaptation is a long-term process and is dependent on specific circumstances.
While a clear picture of successful adaptation may be difficult to pin down, our findings suggest that we can identify what it looks like when things go wrong with adaptation planning – and how not to make those mistakes in future.
What is ‘maladaptation’?
Understanding what processes lead to maladaptation and how to avoid it remains the subject of intense discussion.
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Dr Lisa Schipper, Dr Morgan Scoville-Simonds, Dr Katharine Vincent, Prof Siri Eriksen, climate change, maladaptation, carbon brief, adaptation
UNEP: Net-zero pledges provide an ‘opening’ to close growing emissions ‘gap’
The recent net-zero pledges by major emitting countries and the potential for a “green recovery” from the Covid-19 pandemic “presents the opening” for the world to close the growing “gap” between existing commitments and what is needed to limit global warming to meet the Paris Agreement goals.
This is according to the latest UN Environment Programme (UNEP) emissions gap report, published today.
The annual report, now in its 11th year, finds that global emissions will fall in 2020 due to Covid-19 related disruptions. But it also shows starkly how quickly the 1.5C goal is slipping out of reach, as well as how limiting global warming to the “well below” 2C goal is becoming more difficult with every passing year in which emissions continue to grow.
However, UNEP highlights three areas – the recovery from Covid-19, a new willingness by countries to set ambitious mitigation targets, and the rapid advances in clean energy technologies – which together provide an opportunity to help close this “emissions gap”.
But, in the absence of more structural policy-driven changes, it suggests that emissions will rebound in coming years and the gap between commitments and necessary levels of mitigation will remain as large as it was last year. (Carbon Brief’s archives also include detailed coverage of the UNEP reports in 2014, 2015, 2016, 2017, 2018 and 2019).
This year’s report finds that, by 2030, global greenhouse gas emissions will need to fall by 23% from 2019 levels to put the world on track to “likely” (66% chance) avoid 2C warming above pre-industrial temperatures, by 33% to likely avoid 1.8C warming, and by 56% to likely avoid 1.5C warming.
The existing short-term commitments under the Paris Agreement, on the other hand, imply that emissions will simply plateau, remaining only slightly below 2019 levels by 2030.
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Analysis: World has already passed ‘peak oil’, BP figures reveal
The world has already passed “peak oil” demand, according to Carbon Brief analysis of the latest energy outlook from oil major BP.
The 2020 edition of the annual outlook reveals – albeit indirectly – that global oil demand will not regain the levels seen last year. It adds that demand could soon fall rapidly in the face of stronger climate action – by at least 10% this decade and by as much as 50% over the next 20 years.
The latest outlook was delayed by six months so that it could reflect the unprecedented impact of the coronavirus pandemic. The delay also reflects BP’s plans, set out over the course of this year, to reach net-zero emissions by 2050 – as an “integrated energy company”, rather than an oil major.
This means that alongside its conservative “business-as-usual” scenario – in which demand for gas continues to rise indefinitely – BP has also looked at the effect of stronger climate action. In its “rapid” and “net-zero” scenarios, coal and oil see fast declines, while gas peaks by 2025 or 2035.
Although the net-zero focus is new, Carbon Brief analysis shows the outlook continues the trend of previous editions, by cutting the prospects for fossil fuels while raising the bar for renewables.
‘Peak oil’
Global oil demand has doubled over the past 50 years, reaching around 100m barrels per day in 2019, equivalent to an annual energy consumption of 192 exajoules (EJ).
In earlier editions of the BP outlook, global oil demand was expected to continue rising steadily. Indeed, successive editions had raised the outlook for oil, shown in blue lines in the chart below.
By 2018, BP’s outlook started to foresee an end to the upwards march for oil, with demand peaking by the mid-2030s. But the downwards revision in this year’s edition is much more dramatic (red lines), showing demand having already peaked in 2019, with large potential downside risks.
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Guest post: Why low-end ‘climate sensitivity’ can now be ruled out
Guest post: Why low-end ‘climate sensitivity’ can now be ruled out
After four years of labour and detailed discussions by an international team of scientists, we are able to quantify better than ever before how the world’s surface temperature responds to increasing CO2 levels.
Our findings, published in Reviews of Geophysics, narrow the likely range in “equilibrium climate sensitivity” (ECS) – a measure of how much the world can be expected to warm for a doubling of CO2 above pre-industrial levels.
Constraining ECS has remained a holy grail in climate science ever since US meteorologist Jules Charney suggested a possible range of 1.5C to 4.5C in his 1979 report. His estimate was largely based on the world’s first two global climate models, which gave different estimates of 2C and 4C when they performed a simple experiment where atmospheric CO2 levels were doubled.
Since then, despite more than 40 years of research, much improved understanding of atmospheric processes, as well as many more detailed observations, this range has stubbornly persisted.
Now, bringing together evidence from observed warming, Earth’s distant past and climate models, as well as advances in our scientific understanding of the climate, our findings suggest that the range of ECS is likely to be between 2.6C and 4.1C.
This narrowed range indicates that human society will not be able to rely on a low sensitivity to give us more time to tackle climate change. But the silver lining to this cloud is that our findings also suggest that very high ECS estimates are unlikely.
Stubbornly wide range
How sensitive the Earth’s climate is to increasing atmospheric CO2 is a fundamental question for climate science. It essentially dictates how much the Earth’s surface will warm in response to human-caused CO2 emissions.
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Analysis: How ‘carbon-cycle feedbacks’ could make global warming worse
Analysis: How ‘carbon-cycle feedbacks’ could make global warming worse
Scientists making climate-change projections have to deal with a number of uncertainties.
The amount of global warming will depend on the magnitude of future emissions, which, in turn, depends on how society grows and develops. The rate of warming will also depend on how sensitive the climate is to increased atmospheric greenhouse gases.
Yet climate change also depends on an under-appreciated factor known as “carbon-cycle feedbacks”. Accounting for uncertainties in carbon-cycle feedbacks means that the world could warm much more – or a bit less – than is commonly thought.
The carbon cycle is the collection of processes that sees carbon exchanged between the atmosphere, land, ocean and the organisms they contain. “Feedbacks” refer to how these processes could change as the Earth warms and atmospheric CO2 concentrations rise.
The commonly used warming projections – those highlighted in Intergovernmental Panel on Climate Change (IPCC) assessment reports – include a single best-estimate of carbon-cycle feedbacks. But they do not account for the large uncertainties in these estimates.
These uncertainties are “one of the dominant sources” of divergence between different model projections, according to Dr Ben Booth and colleagues at the Met Office Hadley Centre.
Climate campaigners, such as Greta Thunberg, have also expressed concern that climate projections typically do not fully incorporate the potential range of carbon-cycle feedbacks.
This article explores the implications of carbon-cycle feedback uncertainties by examining a number of modelling studies conducted by scientists over the past decade. These studies give a similar central estimate of carbon-cycle feedbacks to those used in IPCC projections.
But, at the high end, the results show these feedbacks could push atmospheric concentrations of greenhouse gases much higher – meaning more warming – from the same level of emissions.
Analysis for this article shows that feedbacks could result in up to 25% more warming than in the main IPCC projections.
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Guest post: The irreversible emissions of a permafrost ‘tipping point’
Guest post: The irreversible emissions of a permafrost ‘tipping point’
Across vast swaths of the northern hemisphere’s higher reaches, frozen ground holds billions of tonnes of carbon.
As global temperatures rise, this “permafrost” land is at increasing risk of thawing out, potentially releasing its long-held carbon into the atmosphere.
Abrupt permafrost thaw is one of the most frequently discussed “tipping points” that could be crossed in a warming world. However, research suggests that, while this thawing is already underway, it can be slowed with climate change mitigation.Tipping pointsThis article is part of a week-long special series on “tipping points”, where a changing climate could push parts of the Earth system into abrupt or irreversible change
Yet, what is irreversible is the escape of the carbon that has been – and is being – emitted. The carbon released from permafrost goes into the atmosphere and stays there, exacerbating global warming.
In short, what happens in the Arctic does not stay in the Arctic.
Permafrost and the global climate
Permafrost is ground that has been frozen for at least two consecutive years. Its thickness ranges from less than one metre to more than a kilometre. Typically, it sits beneath an “active layer” that thaws and refreezes every year.
A warming climate puts this perennially frozen ground at risk. When temperatures rise, permafrost thaws – it does not melt.
There is a simple analogy: compare what happens to an ice cube and a frozen chicken when they are taken out of the freezer. At room temperature, the former will have melted, leaving a small pool of water, but the chicken will have thawed, leaving a raw chicken. Eventually, that chicken will start to decompose.
This is exactly what happens to permafrost when temperatures increase. One quarter of the landmass of the northern hemisphere is underlain by permafrost, which acts like Earth’s gigantic freezer and keeps enormous amounts of organic matter frozen.
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Q&A: How is Arctic warming linked to the ‘polar vortex’ and other extreme weather?
Q&A: How is Arctic warming linked to the ‘polar vortex’ and other extreme weather?
The past week has seen some brutal weather hitting the US and Canada. With cold Arctic air plunging south down to the US midwest, six states have seen temperatures lower than the south pole and at least eight people have died due to the extreme cold.
The UK, too, is braced for snow this week, but nothing close to the scale seen in the US.
The very cold weather prompted President Trump to tweet: “What the hell is going on with Global Waming? [sic].” This followed an earlier tweet that it “wouldn’t be bad to have a little of that good old fashioned Global Warming right now!”
Trump’s comments received widespread derision from scientists and the media, with many articles pointing out that Trump is confusing short-term weather events with long-term climate, and that extreme cold weather still occurs in a warming world.
The cold, snowy weather has also been accompanied by a flurry of stories about the “polar vortex” and how it can bring extreme weather to the northern hemisphere mid-latitude regions of North America, Europe and Asia. But that is not the only way that the Arctic can affect conditions further south.
Over the past decade or so, a growing body of research has proposed ways in which rapid Arctic warming can lead to harsh winters, summer heatwaves and even floods and droughts across the mid-latitudes.
Some scientists say that climate change and Arctic sea ice loss are the root cause of these events, but others are more circumspect.
In this detailed Q&A, Carbon Brief speaks to scientists about the potential connections between Arctic warming and extreme weather across the mid-latitudes, what those theories look like, and how the evidence measures up.
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Ten charts show how the world is progressing on clean energy
Rapid progress towards clean energy is needed to meet the global ambition to limit warming to no more than 1.5C above pre-industrial temperatures.
But how are countries doing so far? In our Energy Revolution Global Outlook report, written with colleagues at Imperial College London and E4tech – and published by Drax– we rank progress in 25 major world economies.
Our report provides a league table of their efforts to clean up electricity generation, switch from oil to electric vehicles, deploy carbon capture and storage, eliminate fossil fuel subsidies and tackle energy efficiency.
The ten charts below compare these 25 countries today and their progress over the last decade.
Progress on clean electricity
Electricity has been the fastest sector of the economy to decarbonise as countries move away from coal and embrace low-cost renewables. Yet the average carbon intensity of electricity worldwide has fallen only 7% in the last decade to 450 grams of CO2 per kilowatt hour (gCO2/kWh).
The chart below maps the carbon intensity of electricity generation around the world and ranks the 25 major economies covered by our report. These countries include the G7 group of rich nations along with Brazil, Russia, India, China and South Africa (the “BRICS”) and others. These countries account for 80% of global population, 77% of global GDP and 73% of the world’s CO2 emissions.
Individual countries range from having virtually zero-carbon electricity (in the Nordics, France and New Zealand, left-hand columns in the lower chart) up to near-total reliance on coal (in South Africa and Poland, on the far right).
The carbon intensity of electricity generation during 2017, in grams of CO2 per kWh. The map includes all countries for which data is available. The bar chart ranks 25 major economies including all G7 and BRICS countries. Bar widths represent the amount of electricity consumed in each country, with a minimum width so that smaller countries are still visible. Source: Drax 2018.
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IEA: Clean energy transition makes reforms ‘inescapable’ for oil states
A changing energy system is posing “critical questions” for many of the world’s largest oil and gas producing countries, the International Energy Agency (IEA) says.
The rise of shale gas and oil in the US, global improvements in energy efficiency, and the response to climate change are leading to “sustained pressure” on countries that rely heavily on hydrocarbon revenues, it says.
In a new report, the IEA explores what these changing dynamics mean for six major oil-producing states and the consequences of a global push to meet climate change goals.
Oil producers
The report focuses on “producer economies”: large oil and gas producers which rely on hydrocarbon exports for a large portion of their national budgets.
Many of these countries are shown (in purple) in the chart, below. The report narrows in on six of these – Iraq, Nigeria, Russia, Saudi Arabia, United Arab Emirates (UAE) and Venezuela – chosen for their range of circumstances.
Oil and gas exports as a share of total exports (x-axis) and oil and gas revenue as a share of fiscal revenue (y-axis) in selected countries in 2017. Source: IEA Outlook for Producer Economies 2018
In these six countries, between 40% and 90% of government revenues come from oil and gas income. These earnings make up a similar share of the countries’ total exports.
This somewhat precarious position has been exposed by low oil prices since 2014. This has seen many of these countries facing recessions, falling incomes, budgetary deficits and even social unrest.
The “shale revolution” and long-term uncertainty over demand for oil and gas are “intensifying pressures for change” in these countries, the report says. It adds:
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Q&A: Why cement emissions matter for climate change
If the cement industry were a country, it would be the third largest emitter in the world.
In 2015, it generated around 2.8bn tonnes of CO2, equivalent to 8% of the global total – a greater share than any country other than China or the US.
Cement use is set to rise as global urbanisation and economic development increases demand for new buildings and infrastructure. Along with other parts of the global economy, the cement industry will need to dramatically cut its emissions to meet the Paris Agreement’s temperature goals. However, only limited progress has been made so far.
Reducing emissions from cement. Infographic by Rosamund Pearce for Carbon Brief.
What is cement?
Cement is used in construction to bind other materials together. It is mixed with sand, gravel and water to produce concrete, the most widely used construction material in the world. Over 10bn tonnes of concrete are used each year.
The industry standard is a type called Portland cement. This was invented in the early 1800s and named after a building stone widely used in England at the time. It is used in 98% of concrete globally today, with 4bn tonnes produced each year.
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Clean energy investment ‘must be 50% higher’ to limit warming to 1.5C
An extra $460bn per year needs to be invested on the low-carbon economy globally over the next 12 years to limit global warming to 1.5C, a new paper says.
This is 50% higher than the additional investment needed to meet a 2C limit, the paper says. It is the first to assess the difference in investments and monetary flows between the two temperature goals of the Paris Agreement, the lead author tells Carbon Brief.
The paper also finds a far faster increase in low-carbon energy and energy efficiency investment would be needed to limit warming to 1.5C. Meanwhile, coal investment would not change substantially between a 1.5C and 2C scenario, the lead author says, since a dramatic downscaling of coal investments is already required to meet the 2C goal.
Financial flows
The Paris Agreement says countries should scale up finance to the low-carbon economy. Article 2.1(c) of the deal commits signatories to:
“Making finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development.”
The new paper, published today in Nature Energy, aims to quantify the scale of financial flows that may be required to meet the overarching temperature goals of the Paris deal. It assesses how much would be needed for four scenarios.
In the first, countries meet the targets laid out in their current individual climate pledges (“nationally determined contributions”, or NDCs). The second looks at meeting the Paris goal of limiting global warming to “well below 2C”. The third scenario considers a world where the aspirational Paris target of limiting warming to 1.5C is met. These are compared to a business-as-usual scenario with no further tightening of current climate and energy policies.
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Analysis: ‘Global’ warming varies greatly depending where you live
As part of the Paris Agreement on climate change, the international community committed in 2015 to limit rising global temperatures to “well below” 2C by the end of the 21st century and to “pursue efforts to limit the temperature increase even further to 1.5C”.
However, these global temperature targets mask a lot of regional variation that occurs as the Earth warms. For example, land warms faster than oceans, high-latitude areas faster than the tropics, and inland areas faster than coastal regions.
Furthermore, global human population is concentrated in specific regions of the planet.
Here, Carbon Brief analyses how much warming people will actually experience where they live, both today and under future warming scenarios.
The warming experienced by people is typically higher than the global average warming. In a world where warming is limited to “well below” 2C about 14% of the population will still experience warming exceeding 2C. In the worst-case scenario of continued growth in emissions, about 44% of the population experiences warming over 5C – and 7% over 6C – in 2100.
Warming is not globally uniform
Different parts of the world respond in different ways to warming from increasing greenhouse gas concentrations. For example, ocean temperatures increase more slowly than land temperatures because the oceans lose more heat by evaporation and they have a larger heat capacity.
High-latitude regions – far north or south of the equator – warm faster than the global average due to positive feedbacks from the retreat of ice and snow. An increased transfer of heat from the tropics to the poles in a warmer world also enhances warming. This phenomenon of more rapidly warming high latitudes is known as polar amplification.
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