In the latest article in a series on the world’s key emitters Carbon Brief looks at the US, which, to date, has contributed more to human-caused climate change than any other nation.
The country is the top producer and consumer of both oil and natural gas, plus it has the world’s second largest fleet of coal-fired power plants. It also has the largest nuclear and second largest renewable capacity.
Today, the US is only the second largest emitter of greenhouse gases, but over the course of history it has cumulatively produced more CO2 than any other nation. Its citizens have carbon footprints that are roughly three times the global average.
Following the election of Joe Biden as president at the end of 2020, many observers now hope that his administration will fulfil its election pledge to prioritise climate action across its activities.
- Paris pledge
- Climate policies and laws
- Oil and gas
- Impacts and adaptation
The US is one of the world’s largest democracies and by far the world’s largest economy, with a GDP in 2019 the size of China, Japan and Brazil combined.
It is a federal republic consisting of 50 states, the district of Washington DC and five island territories. Lawmaking and enforcement are shared across state and national governments.
The US has a two-party system dominated by the centre-left Democrats and the centre-right – yet increasingly right-wing – Republicans.
After victory in last year’s presidential election the Democrat Joe Biden has proposed an ambitious framework to tackle climate change, develop green infrastructure and promote environmental justice, while rebuilding the economy following the Covid-19 pandemic.
This is a marked contrast to his predecessor Donald Trump, a Republican who spent his term dismantling environmental regulations and vocally opposing climate action.
These differences reflect the partisan nature of climate action in the US.
In recent decades, Democrats have broadly been more in favour of addressing climate change, both at a federal level and in states they govern. Republicans have overwhelmingly opposed environmental regulation and even denied the existence of climate change.
Polling by the Pew Research Centre has found that while there is broad support for climate measures, such as tree planting and renewable power, people’s views on the cause of climate change are deeply divided along party lines.
While 72% of Democrats in 2020 said they think human activity contributes a great deal to climate change, only 22% of Republicans agreed.
Climate scepticism is prevalent in the US, fuelled in part by highly polarised media coverage. A Business Insider story in 2019 concluded 130 members of Congress at that time had “doubted or denied climate change” and all but one of them was Republican.
It is worth noting that this partisan divide has not always existed, but has been growing since the late 1990s. Carbon Brief’s timeline of the annual presidential state-of-the-union addresses shows how the issue has shifted in significance since 1989.
In 1970, the Republican administration of Richard Nixon oversaw the creation of various agencies and policies that today form the bedrock of US climate action, including the Environmental Protection Agency (EPA) and the Clean Air Act.
While there have been various energy and climate measures implemented since then, both at state and national levels (see: Climate policies and laws), the US still lacks a comprehensive federal climate policy.
Federal power is divided between the executive, which consists of the president and their cabinet, the judiciary – the Supreme Court and other federal courts – and the two chambers of Congress.
The House of Representatives is the lower house of Congress, consisting of 435 members with each state allocated a number based on its population size. The Senate is the upper house, with two senators for each state.
Together, they are responsible for developing and passing legislation, but difficulties in securing Republican support in Congress for comprehensive climate action mean the responsibility has often fallen on the executive branch. (Republican support is often necessary even with Democratic majorities in both houses, owing to the need for 60 votes to cut off debate and move legislation forward in the Senate.)
The executive branch can implement existing law through regulations and programmes, which, in practice, has meant bodies such as the EPA and the departments of energy and transport introducing measures to cut emissions and improve energy efficiency.
In some cases the president can also issue “executive orders” to the federal government, which do not require congressional approval. These have been used by successive presidents to join, exit and then re-enter the Paris Agreement, among other things.
Federal courts also play a role in climate action by interpreting existing laws, limiting the scope of executive orders, and providing means for states, businesses and citizens to challenge measures in place.
State governments can play a significant role in climate and clean energy policies. While state attitudes to these topics vary considerably, most have introduced measures to boost renewable power and energy efficiency.
Although an attempt spearheaded by Democrats Alexandria Ocasio-Cortez and Ed Markey to pass such legislation in 2019 failed in the Senate, both supporters and opponents of the deal think it has been highly influential in shaping the Biden administration’s climate policy.
Climate change poses an existential threat to our communities, economy, national security, and environment. Our plan for a Clean Energy Revolution & Environmental Justice will address the climate emergency & protect our communities for generations to come. https://t.co/FbsOsyQkIo— Joe Biden (@JoeBiden) June 20, 2019
In it, the US commits to cutting greenhouse gas emissions 50-52% below 2005 levels by 2030.
This compares with the old target from 2015, set by president Barack Obama, which was to cut greenhouse gas emissions by 26-28% by 2025 compared to 2005.
OFFICIAL— Simon Evans (@DrSimEvans) April 22, 2021
The US is pledging to cut its greenhouse gas emissions to 50-52% below 2005 levels by 2030
That’s equivalent to 41-43% below 1990 levels
(The Obama era pledge for 2025 was equivalent to ~38% below 2005 by 2030)
(added new version of my chart)https://t.co/PUSAoBNEV5 pic.twitter.com/SqAmReb6K5
The new target builds on a previous pledge by Biden to achieve net-zero emissions economy-wide by “no later than 2050”.
It was framed by the administration as a way of pursuing its wider policy agenda such as investing in infrastructure and creating green jobs.
The NDC was also seen by commentators as an important move that would encourage other nations to take stronger action on climate change as well.
In its assessment of the old NDC, Climate Action Tracker (CAT) – an independent analysis of climate pledges produced by three research organisations – described the US commitment as “critically insufficient” for achieving the Paris Agreement temperature goals.
While CAT said Biden’s NDC was “a significant step forward”, it added that the new target is still short of the 57-63% below 2005 levels by 2030 that would be consistent with a 1.5C-compliant pathway for the US.
Trump’s plan to leave the Paris Agreement when he won the presidency in 2016 was met with dismay by the international community, not least because of the enormous contribution the US makes – and has made – to global emissions.
The country’s annual greenhouse gas emissions were 6,534m tonnes of CO2 equivalent (MtCO2e) in 2015, according to data compiled by the Potsdam Institute for Climate Impact Research (PIK).
The 2015 figure is used because this is the most recent year in which a number for emissions from land use, land-use change and forestry (LULUCF) is available from this database.
Since then emissions have fallen slightly, although not as rapidly as in previous years. According to the latest EPA data, in 2019 total gross US greenhouse gas emissions were 6,558MtCO2e and net emissions including sinks were 5,769MtCO2e.
This means around 13% of global emissions are produced in the US. Since the start of the industrial era it has been responsible for nearly twice as many emissions as the closest contender, China, which today has a population four times larger than the US.
The nation’s per-capita emissions are also among the highest in the world and roughly three times the global average.
The US is part of the “Umbrella group” during the United Nations Framework Convention on Climate Change (UNFCCC) talks, alongside other developed nations including Australia, Japan and Canada.
A core part of the US strategy has often been to argue that low- and middle-income nations, including China, should be encouraged to cut their emissions. It has also opposed efforts to set “top-down” emissions targets in favour of national sovereignty.
President George H Bush made it clear at the Rio Earth Summit in 1992, where the UNFCCC was established, that ”the American way of life is not up for negotiation”.
When climate agreements have emerged, Democratic US presidents have embraced them, at least publicly, only for their Republican successors to distance themselves.
However, the unanimous passage of the “Byrd-Hagel resolution” in the Senate effectively made US involvement impossible as it stated that the nation should not sign up to any treaties that did not cover developing nations.
When George W Bush took office in the following decade, he explicitly rejected the protocol and the US has never subsequently ratified it. Subsequently, other nations either withdrew, in the case of Canada, or failed to renew their commitments after 2012.
Obama tried to push a new agreement at COP15 in 2009, but the Copenhagen Accord that emerged was not legally binding and the event was widely seen as a failure. The next major moment for a global deal came at COP21 in Paris six years later.
The US was seen as a key driver of a compromise that involved all countries setting non-binding targets determined by the parties themselves. Unlike the Kyoto Protocol, Obama was able to pass it in by executive order and did not need to run it past Congress.
However, in 2017, with Trump as president, the new Republican administration made it clear it intended to withdraw the US from the Paris Agreement. This decision did not come into effect until November 2020 and two months later Biden had reversed it with another executive order.
In terms of its other international obligations, the US is regarded as having fallen short on its climate finance commitments to poorer nations. (The Trump administration also attempted to withdraw funding from the UNFCCC itself.)
Under Obama, the US pledged $3bn to the Green Climate Fund, but had only handed out $1bn before support was withdrawn under Trump. The Biden administration has now proposed spending $1.2bn in his 2022 budget.
According to the World Resources Institute (WRI), “hard work by many members of Congress” ensured overall US climate finance to other international initiatives did not significantly decline under Trump, but as other nations have scaled up spending the US “has still fallen down the rankings”.
After releasing an updated NDC, the Biden administration announced its intention to double US international climate finance by 2024 and triple funding for adaptation, relative to the $2.8bn a year committed during the second half of the Obama administration. The announcement does not mention the Green Climate Fund.
Climate policies and laws
Passed in 1970, the act was originally intended to tackle air pollution and was not designed to address climate change.
However, a 2007 Supreme Court decision known as Massachusetts vs EPA concluded that greenhouse gases “fit well within the Clean Air Act’s capacious definition of ‘air pollutant’”.
Two years later, the EPA issued its “endangerment finding” that concluded greenhouse gases were a threat to public health. This has since formed the basis of the agency’s action to regulate emissions from vehicles and industrial facilities.
However, the Trump administration attempted to repeal the plan and replace it with his far weaker Affordable Clean Energy rule. In early 2021, a federal appeals court ruled that this violated the Clean Air Act, leaving room for the Biden administration to replace it with its own regulations.
Trump’s efforts to unravel his predecessor’s emissions regulations largely hinged on a background dispute over the “social cost” of carbon.
Under Obama, one tonne of CO2 was estimated to cause about $50 in economic damage by 2020, whereas under Trump this cost was set as low as $1. This was used to justify a lax approach to regulating emissions. (It has now been returned to its Obama-era value.)
There have been further efforts to pass more climate-relevant legislation, particularly some form of a cap-and-trade system in which limits are set on emissions and companies are able to buy and sell allowances if they need to exceed these limits.
Notable examples include significant bipartisan efforts between 2003 and 2010 to introduce such an economy-wide system, all of which failed to make it past Congress.
In 2009, for the first time, comprehensive climate legislation passed the US House of Representatives. However, the American Clean Energy and Security Act, known as “Waxman-Markey”, faced strong Republican opposition in the Senate and lobbying by fossil fuel interests and was, ultimately, scrapped.
Similarly, oil-industry lobbyists have been implicated in holding back state initiatives to try and introduce carbon pricing.
Despite these failures, there have been successful examples of regional cap-and-trade systems in the US.
The Regional Greenhouse Gas Initiative (RGGI) was the first mandatory market-based programme in the country designed to cut emissions, established in 2009 to cover power plants across 11 states in the northeastern US.
California’s cap-and-trade programme is one of the world’s largest multi-sectoral emissions trading systems. It covers about 85% of the state’s emissions and is part of a goal to reach economy-wide carbon neutrality by 2045.
Over the years there have also been federal efforts to support clean energy, including the 2005 Energy Policy Act and the 2007 Energy Independence and Security Act, which brought in tax incentives and subsidies for renewables and nuclear power. These have been complemented by state-level policies (See: Renewables).
The George W Bush administration authorised the creation of the Advanced Research Projects Agency-Energy (ARPA-E) in 2007 to promote and fund new energy technologies.
It was subsequently provided with its first funding in Obama’s recovery act and a review of its progress in 2017 found that it has been successful in driving innovation. Biden is now seeking to replicate this success with a new Advanced Research Projects Agency-Climate (ARPA-C) initiative.
The Covid-19 pandemic has indirectly led to new climate policies, including the Consolidated Appropriations Act at the end of a 2020, while Trump was still in power.
This $2.3tn spending package, with $900bn of Covid-19 stimulus, was not expressly a climate bill, but nevertheless included tax breaks for renewables, carbon capture and storage (CCS) initiatives and a phaseout of planet-warming hydrofluorocarbons (HFCs).
Since then, the Biden administration has proposed further stimulus packages, most significantly the $2tn “American Jobs Plan” which focuses on infrastructure and includes a national clean electricity standard as well as billions in subsidies for low-carbon energy and electric vehicles.
The president said the plan would “lead to a transformational progress in our effort to tackle climate change with American jobs and American ingenuity”.
Renewable energy from wood and some hydroelectric dams powered the US during its early industrialisation before being superseded by fossil fuels at the end of the 19th century.
In recent years, renewables have grown into a significant part of the nation’s electricity mix, although they are still dwarfed by coal and gas generation, as the chart below shows.Electricity generation in the US by fuel, 1985-2020 (Terawatt hours). Figures for 2020 are calculated using % change from analysis conducted by the climate thinktank Ember. Source: BP Statistical Review of World Energy 2020 and Ember Global Electricity Review 2021. Chart by Carbon Brief using Highcharts.
The US ranks second in the world for renewable power, with 311 gigawatts (GW) of capacity as of 2020, according to the International Renewable Energy Agency (IRENA). This is about twice as much as Brazil, in third place, but only around a third of China’s capacity.
Together with other renewables, they overtook coal power last year for the first time, with 21% of the electricity mix.
These technologies have been largely sheltered from the economic impact of Covid-19, particularly as wind developers have rushed to meet federal tax incentive deadlines. Solar and wind power are expected to make up 70% of the new capacity coming online in 2021, according to the Energy Information Administration (EIA).
Wind is now the nation’s largest source of renewable power, surpassing hydro in 2019. The US remains the world’s third largest hydropower producer by capacity, after China and Brazil, according to the International Hydropower Association.
A Carbon Brief map from 2017 illustrates how the US renewable energy rollout has been impacted not only by federal and state governments but also geography. Wind installations, for example, are concentrated down the middle of the nation where wind speeds are highest.
Biden has pledged to achieve “100% carbon-free electricity by 2035”. Recent analysis suggests emissions from the US power system are already 52% lower than the EIA predicted they would be back in 2005.
Separately, seven states plus Washington DC and Puerto Rico have legislatively committed to 100% clean electricity by 2050 or earlier, while another eight states have a non-binding 100% goal.
Net-zero targets for 2050 have also been set by some of the nation’s biggest utilities.
(As one paper notes, the US will need to do more than decarbonise electricity to achieve its climate targets. The nation’s building stock, for example, is considerably less energy efficient than other wealthy nations.)
There has been some federal support for renewables (See: Climate policies and laws), notably tax incentives, such as the renewable electricity production tax credit (PTC) and the investment tax credit (ITC), which have played a significant role in expanding wind and solar.
However, state-level policies have also been important. Renewable portfolio standards that require electricity suppliers to provide a certain amount of renewable power have been important in the proliferation of these technologies.
So far, 29 states and Washington DC have one in place, including Republican-dominated states such as Texas. (In fact, Texas has more wind, solar and energy storage capacity than any other state and was one of the first to adopt a renewable portfolio standard.)
Energy efficiency resource standards (EERS) or energy efficiency targets to encourage more efficient generation, transmission and use of electricity by utilities have also been implemented widely. As of 2019, 27 states had EERS in place.
The US is the world’s largest producer of nuclear power, accounting for more than 30% of worldwide nuclear generation of electricity, according to the World Nuclear Association.
Nuclear is also the largest single source of clean power in the US, with 19.5% of generation, according to Ember.
The nation was a pioneer in early nuclear development, with the first commercial nuclear plant built at Shippingport, Pennsylvania, in the late 1950s.
There was talk of a “nuclear renaissance” during the 2000s, spurred on by financial incentives in the government’s Energy Policy Act of 2005.
In 2012, the first nuclear power reactors for decades were approved at the existing Vogtle nuclear power plant in Georgia. These remain the only new reactors under construction, as plans for an additional pair of reactors in South Carolina were abandoned in 2017.
Since then the fracking boom (See: Oil and gas) and resulting low gas prices have discouraged the construction of new nuclear capacity.
As Carbon Brief analysis demonstrated in 2018, competition with gas combined with an ageing nuclear fleet and the availability of low-cost renewables have also put many existing nuclear plants at risk of premature retirement on economic grounds.
Several states have considered expanding their renewable portfolio standards to include other low-carbon sources of power. New York introduced a “zero-emissions credit” system to its clean energy standard specifically to subsidise its nuclear plants.
Nevertheless, US nuclear power is still expected to follow a downward trajectory in the coming years.
In 2021, 5.1GW of nuclear power – 5% of current US capacity – is expected to shut down. The most recent retirement was Indian Point, about 25 miles north of New York City, which previously provided a quarter of the city’s power.
Energy experts have expressed concerns about the impact the shrinking US nuclear fleet could have on the nation’s emissions.
Analysis by the EIA and others suggests that when US nuclear plants have been retired in recent years they have been replaced by fossil fuels. However, others have argued that retiring nuclear capacity saves money that can then be invested in renewables.
In 2019, the thinktank Rhodium Group stated that without “significant changes in federal or state policy” to address competition with low-cost gas, “in the worst-case scenario for nuclear power, 45% of the current fleet could retire by 2025” – around 44GW.
In its analysis the following year, the group noted that Covid-19 had put further pressure on nuclear plants due to their high operating costs.
The Biden administration’s policy on nuclear power is essentially a continuation of Trump’s, albeit framed around tackling climate change rather than energy security. The president’s platform mentions using ARPA-C to develop advanced nuclear reactors “that are smaller, safer and more efficient at half the construction cost of today’s reactors”.
As of January 2021, the US had 234GW of operating coal plants, the world’s second largest fleet and about 11% of the global total, according to the Global Coal Plant Tracker. This is around a quarter the size of China’s capacity.
According to analysis by Ember, last year India produced more electricity from coal than the US, which still generated 774TWh and was the third largest coal power generator.
Five states account for about 71% of total US coal production, with Wyoming alone responsible for 39%.
Coal was a key driver of US industrialisation and was widely used in homes and transport, but today around 90% of coal consumption is for electricity generation and nearly all the rest is used in industry. (Around two-thirds of steel production in the US relies on electric arc furnaces, which, unlike blast furnaces, do not require coal as a raw material.)
Following a peak in 2007, coal consumption and production have both roughly halved over the past decade. There are currently no new coal plants in the pipeline and the chances of any emerging are seen as unlikely.
Most of the electricity previously generated by burning coal has been replaced by gas – which has replaced it as the largest source of power – and, to a lesser extent, renewables.
The fuel has been squeezed out by alternatives as demand has remained flat for more than a decade, breaking the previous trend of year-on-year increases tied to economic growth.
The nation does not have a phaseout date for coal power, but the pace of plant decommissioning has sped up in recent years, with 126GW of capacity retired between 2000-2020. Another 29GW of planned capacity has been shelved or cancelled during this period.
Nearly a third of the remaining coal fleet is expected to close by 2030, according to Global Energy Monitor.
When Trump came to power he claimed he would bring an end to the previous administration’s “war on coal”, but its downward spiral has continued regardless.
Despite Trump’s rollback of the Clean Power Plan, utilities still said they intended to go ahead with coal closures and while thermal coal exports hit record highs during his presidency – mainly due to Asian demand – there is evidence this market is also weakening.
During the first presidential debate last year, Biden declared “nobody’s going to build another coal-fired power plant in America”. His administration has halted new leases for coal, oil and gas extraction on federal lands.
Coal’s decline in the US has been attributed to various factors, including economics. The fossil fuel is simply no longer the cheapest way to generate electricity as the price of gas (see: Oil and gas) and renewables declines.
Environmental regulations have also had an impact. A recent study found the Cross State Air Pollution Rule, which requires states to cut soot and smog that blows across state lines, had the “greatest aggregate impact on coal retirements”. Mercury and Air Toxics Standards have also reportedly impacted coal generation.
The same paper also concluded that environmental campaigning played a considerable role, notably Sierra Club’s Beyond Coal campaign which has made use of lawsuits targeted at individual power plants.
State-level politics also impacts the speed of shutdowns, with the Los Angeles Times reporting that, for utilities in western states, half the coal plants without retirement dates are in Montana, Utah and Wyoming – states led by “fossil fuel-friendly politicians with little or no regulation requiring cleaner energy”.
In addition, as many coal plants in the US are operated by regulated utilities, there is evidence that they are running in some energy markets even when they are losing money, with costs being passed onto customers.
Oil and gas
The US is the world’s top producer and consumer of both oil and fossil gas, according to the latest figures from the EIA.
Since 2015, the year the Paris Agreement was signed, Ember analysis found that global gas generation increased by 576 terawatt-hours (TWh), of which around half was from the US.
Oil has been central to US domestic and foreign policy for decades.
The “Carter doctrine” of 1980 made it clear the US would use military force to defend the oil fields of the Persian Gulf against external threats. The nation’s involvement in Middle Eastern conflicts since then has widely been viewed as related to its oil interests.
Its current status as the top oil and gas producer is largely the result of the US “shale revolution”.
This was part of efforts to establish the nation as “energy independent”, meaning it would not be reliant on potentially hostile foreign powers for oil, in a bid to avoid the oil crises of the 1970s. (The US remains a major importer of crude oil.)
In response to the 1973 oil embargo by the Organization of Arab Petroleum Exporting Countries, the US government began adopting a series of policies, including energy-related R&D programmes to develop new sources of fossil gas.
Both oil and gas production in the US had seemingly peaked in 1970 and entered a period of decline that lasted until the mid-2000s.
However, investment in new extraction techniques – specifically horizontal wells and hydraulic fracturing, known as fracking – have made fossil fuel production less expensive and opened up large “unconventional” reserves, particularly of shale gas.
Gas has helped to bring down US emissions as it has edged out coal in the power sector. However, many experts and campaigners have raised concerns about replacing one fossil fuel with another. (Research has also suggested that the impact of fracking on cutting emissions may have been overstated.)
The US shale gas boom has also been linked to a spike in the potent greenhouse gas methane – which leaks from operations – in the planet’s atmosphere.
The EPA under Obama produced its first-ever regulations to cut methane emissions from the oil and gas industry, a move then-administrator Gina McCarthy described as “common sense”.
Subsequently, a requirement for companies to fix methane leaks was one of the final environmental policy rollbacks engineered by the Trump administration. The action was opposed, even by some oil and gas companies.
Biden has since committed the US once again to tackling methane. The Obama administration pledged to cut methane emissions by 45% below 2012 levels by 2025 and the new EPA administrator Michael Regan has suggested Biden’s target could exceed that.
The US is home to two of the world’s largest oil and gas companies, ExxonMobil and Chevron, neither of which have committed to tackling climate change to the extent of their European counterparts.
Oil and gas activities in the US have long been the targets of environmental campaigners. Major pipelines, such as Dakota Access and Keystone XL, have faced consistent opposition from climate and Indigenous rights activists, as well as landowners who oppose the infrastructure.
Another key battleground has been the Arctic National Wildlife Refuge in Alaska, which has been the subject of dozens of attempts by Congress to allow drilling for oil, culminating in success under the Trump administration.
Upon becoming president, Biden signed an executive order revoking the permit for Keystone XL and placed a moratorium on drilling in the Arctic.
This was part of a broader suite of pledges by the new administration to scale back fossil fuel support, including an end to finance for fossil fuels overseas.
However, despite pressure from fellow Democrats as well as claims made by his political opponents, Biden has said he does not intend to ban fracking, stating during the election that he supported it to help “transition to only net-zero emissions”, but wishes to “gradually move away” from it.
Biden’s approach to fossil fuels is in keeping with his broader pledge to address environmental justice.
A key argument from activists is that fossil fuel infrastructure and the resulting public health impacts disproportionately impact poor communities and people of colour in the US.
Finally, the US is also a major exporter of fossil fuels and in 2021 its exports of liquefied natural gas (LNG) to major markets in China, Japan and South Korea reached record levels. One study found that more than half the power-sector emissions avoided during the shale gas boom may have been transferred overseas in the form of rising coal exports.
Cars, vans and small trucks make up the most significant chunk of these emissions, at 59%, and larger trucks and lorries make up 23%.
Aircraft make up 9% of transport emissions and while the EPA finalised its first-ever aviation emissions rules last year it is not projecting any emission reductions as the modifications to planes it calls for would have happened anyway.
The US dominated the automobile industry for decades and is still home to the “big three” car companies, General Motors, Ford and Chrysler. The Californian company Tesla has been recognised as playing a critical role in advancing the electric vehicles industry.
Based on data from the EV-Volumes database for 2020 and the International Energy Agency for previous years, the US is home to around 17% of the 10.4m electric vehicles on the road. As of 2019, more than half the world’s 11,200 hydrogen fuel cell cars were located in California.
Billions of dollars in Biden’s Covid-19 stimulus plans have been set aside to promote electric vehicles but also to improve bus and rail networks. As it stands, the nation’s public transport infrastructure is widely recognised as being less effective than its European and Asian counterparts.
US vehicles tend to be larger, heavier and less efficient than those in other wealthy nations. Fuel efficiency improvements have had a significant impact on road emissions in the US and have been a central part of debates around climate policy.
Over the past four decades, one study found that fuel savings in cars and other “light duty” vehicles have saved 17bn tonnes of CO2 (GtCO2) over the past 45 years.
The corporate average fuel economy (CAFE) standard, set in miles per gallon, was established by the National Highway Traffic Safety Administration (NHTSA) in the 1970s following the oil embargo, in a bid to save fuel and make the US less dependent on imports.
Separately, following the Massachusetts vs EPA Supreme Court ruling in 2007, the EPA was able to begin setting standards for grammes of CO2 emitted per mile.
In 2010, the Obama administration oversaw the creation of a coordinated set of standards by these organisations that would both save fuel and cut emissions. Previously, the administration had provided a bailout to the US auto industry while stipulating that companies had to invest in improving vehicle efficiency.
The NHTSA and EPA also worked with the state of California, which had been able to set its own stricter standards under the Clean Air Act. (The Bush administration had previously actively lobbied against this ability.)
In 2012, the government issued its second set of rules that required automakers to nearly double the average fuel economy of new cars and trucks by 2025, measures it said would cut emissions from cars and light trucks in half over this period.
However, when the Trump administration took over it announced plans to roll back regulations, freezing standards at 2020 levels and stopping California from setting its own standards.
Since taking power, Biden has ordered agencies to revisit this decision alongside other environmental rollbacks brought in by the last administration.
Earlier this year, California announced that it will require all new cars and trucks sold in the state to be zero-emissions by 2035, a move that could cut the state’s emissions by 35%. Washington state may go even further with a 2030 target.
Another key policy for transport emissions is the Renewable Fuel Standard, enacted by Congress in 2005.
This required a certain volume of renewable alternatives, such as ethanol, to be incorporated into petroleum-based fuels, once again partly in an effort to reduce reliance on foreign oil. Most motor fuel now sold in the US contains 10% ethanol.
The standard also had a secondary goal of cutting emissions.
However, according to the US Government Accountability Office it has had “little effect”, largely because advanced biofuels that cut emissions more effectively are not being used in line with expectations.
Agriculture and forests
The US is the largest exporter of agricultural products globally, shipping 20% of its produce abroad. Food and related industries make up a 5.2% share of its GDP and more than 10% of US employment comes from agriculture and the businesses it supports.
Despite gains in efficiency, emissions from farms have been steadily rising and around 10.5% of total US greenhouse gases come from agriculture, according to government figures.
Besides making a significant contribution to climate change, US agriculture is also expected to feel its effects (see: Impacts and adaptation), with the US Department of Agriculture warning of “unprecedented challenges” for the sector in a 2013 report.
Corn is the nation’s most significant grain, with more than 90m acres of crops covering the American Corn Belt in the Midwest and Great Plains. More corn is produced in the US than in the whole of Asia.
Much of the growth in corn production is the result of expanding ethanol demand in the transport sector, which now accounts for nearly 40% of total corn use.
However, following a period of growth ethanol production has slowed down in recent years. The agricultural industry has attributed this to the Trump administration’s trade war with China – a major importer of US ethanol – and the decision to give small refineries exemptions from their obligation to use renewable fuels.
Under Trump, the agriculture department announced its Agriculture Innovation Agenda, an initiative to “stimulate innovation so that American agriculture can achieve the goal of increasing US agricultural production by 40% while cutting the environmental footprint of US agriculture in half by 2050”.
According to the FAO, as of 2020 the US had the fourth highest forest area in the world with 310m hectares. Despite a long history of deforestation, over the past decade there has been extensive tree planting and US forest area has increased by 0.03% on average every year.
Nevertheless, logging operations in south-eastern states have come under heavy criticism. According to a 2019 report by the Natural Resources Defense Council (NRDC), global demand for wood pellets to fuel biomass plants, such as Drax power station in the UK, is “devastating” these hardwood forests.
WRI analysis suggests 60bn new trees could be planted by 2040 across the nation, removing the equivalent of emissions from the entire agricultural sector each year.
Impacts and adaptation
The US covers a vast area of land and a variety of climatic conditions stretching from the freezing tundra of Alaska to the deserts along the Mexican border.
The annual mean temperature of the contiguous US – all the states, excluding Alaska and Hawaii – has already risen by around 1.2C since the period of 1895-1915.
The US National Climate Assessment, released in 2018, stated that:
“The impacts and costs of climate change are already being felt in the US, and changes in the likelihood or severity of some recent extreme weather events can now be attributed with increasingly higher confidence to human-caused warming.”
More events including heatwaves, flooding and storms that have been influenced by climate change can be seen in this Carbon Brief map.
One measure of the increasing severity of these impacts is the rate of so-called “billion dollar disasters” relating to climate and weather.
In 2016, residents of an indigenous Inupiat village voted to relocate their community from an island in Alaska that had been vanishing due to erosion and flooding. A similar situation in Louisiana has seen coastal “refugees” relocated as their homes are inundated with water.
The Pentagon has identified climate change as a national security priority and a 2019 report by the Department of Defense examined the impact of climate change on military activities. (The department itself has an emissions footprint comparable with a medium-sized country.)
In 2013, during the Obama administration, the president signed an executive order calling on every federal agency to release a climate change adaptation plan. The EPA published a plan in response to this request, as did other key agencies, such as the transport, defence and energy departments.
As captured by the Georgetown Climate Centre, many state and local governments have also released their own climate adaptation plans, particularly those in coastal regions.
The “resilience council” that emerged from Obama’s executive order issued guidance to the government on climate adaptation, but, ultimately, the order was rolled back by the Trump administration, putting these efforts on pause.
Upon taking power earlier this year, a Biden executive order reinstated Obama’s efforts in this area, as part of his campaign promise to “define the climate adaptation agenda”.
Graphic by Joe Goodman for Carbon Brief.
Data for energy consumption comes from BP Statistical Review of World Energy 2020. Unlike previous country profile infographics, exajoules (EJ) have been used instead of millions of tonnes of oil equivalent (mtoe) as the unit of energy consumption, in line with BP updating its energy outlook units.
Data for greenhouse gas emissions by sector is a combination of two datasets compiled by the Potsdam Institute for Climate Impact Research (PIK) and EDGAR.
Values for methane (CH4), nitrous oxide (N2O) and fluorinated gases cover all sectors, including LULUCF, and come from the PIK primap database v2.2. Values for greenhouse gas emissions from LULUCF also come from the PIK primap database, however these are only available to 2015, from the earlier v1.2 of the database. Note that LULUCF data for 2015 is an extrapolation made by PIK from previous years.
The remaining values come from the EDGAR CO2 emissions database. The EDGAR categories described in full are as follows: Buildings (non-industrial stationary combustion: includes residential and commercial combustion activities); Transport (mobile combustion: road and rail and ship and aviation); Non-combustion (industrial process emissions a1nd agriculture and waste); Industry (industrial combustion outside power and heat generation, including combustion for industrial manufacturing and fuel production); Power & heat (power and heat generation plants).
Combining greenhouse gas emissions in 2015 (bar LULUCF) from PIK primap 2.0 database and LULUCF emissions in 2015 from PIK database v1.2 also shows the US has the world’s second largest greenhouse gas emissions (6,534MtCO2e), including LULUCF, in 2015. Using this data allows for comparison with previous country profiles in this series.
Per capita emissions in 2015 come from combining the above 2015 figure for greenhouse gas emissions and the US population in 2015 from the World Bank.
The US pledge to reduce its emissions by 50-52% from 2005 levels by 2030 was announced by the White House in April 2021.
The Carbon Brief Profile: United States
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