的Carbon Brief Profile: United States

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.

的country isthe topproducer and consumer of both oil and natural gas, plus it has the world’ssecond largestfleet of coal-fired power plants. It also has thelargestnuclear andsecond largestrenewable capacity.

Today, the US is only the second largest emitter of greenhouse gases, but over the course of history it has cumulatively producedmore CO2than any other nation. Its citizens have carbon footprints that are roughlythree timesthe global average.

Climate change is ahighly divisiveissue in US politics and comprehensive government action has routinely beenblockedby members of theRepublican Party.

Followingthe electionof Joe Biden as president at the end of 2020, many observers nowhopethat his administration will fulfil its election pledge to prioritise climate action across its activities.

• Politics
• Paris pledge
• Climate policies and laws
• Renewables
• Nuclear
• Coal
• Oil and gas
• Transport
• Agriculture
• Impacts and adaptation

Infographic by Joe Goodman.

Politics

的US is one of the world’s largest democracies and by far the world’s largest economy, with a GDPin 2019the 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.

的US has a two-party system dominated by the centre-left Democrats and the centre-right – yetincreasingly right-wing– Republicans.

Aftervictoryin last year’s presidential election the Democrat Joe Bidenhas proposedan ambitious framework to tackle climate change, developgreen infrastructure和促进环境正义,而rebuilding the economy following the Covid-19 pandemic.

This is a marked contrast to his predecessor Donald Trump, a Republican who spent his termdismantlingenvironmental regulations and vocally opposing climate action.

的se 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 statesthey govern. Republicans haveoverwhelminglyopposed environmental regulation and even denied the existence of climate change.

Pollingby thePew Research Centrehas 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, fuelledin partby highly polarised media coverage. ABusiness Insiderstory 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 hasbeen growingsince the late 1990s.亚慱官网’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 Nixonoversawthe creation of various agencies and policies that today form the bedrock of US climate action, including theEnvironmental Protection Agency(EPA) and theClean 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 USstill lacksa comprehensive federal climate policy.

Federal poweris dividedbetween 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.

Each branchhas its own responsibilities, allowing a system of “checks and balances” that is intended to prevent any one branch from wielding too much power.

的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, butdifficulties insecuringRepublican supportin 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 tothe need for 60 votes to cut off debate and move legislation forward in the Senate.)

行政部门可以实现现有法律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 theParis Agreement, among other things.

Federal courtsalso playa 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 asignificant rolein climate and clean energy policies. While state attitudes to these topics vary considerably,most haveintroduced measures to boost renewable power and energy efficiency.

As part of theUS Climate Alliance, a bipartisan coalition of state governors, 25 states and Washington DChave setclimate targets to “advance the goals” of the Paris Agreement.

Fossil fuel companiesare knowntolobbyUS politicians extensively and havebeenaccusedof exerting considerable influence over the nation’s climate policy.

Finally, the concept of a “green new deal” – a reference to president Franklin D Roosevelt’s “new deal” in the 1930s – has risen to prominence in recent years.

Although an attempt spearheaded by Democrats Alexandria Ocasio-Cortez and Ed Markey to pass such legislation in 2019failedin the Senate, bothsupportersandopponentsof 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

Central to the green new deal is the concept ofenvironmental justiceand a “just transition” for fossil fuel workers, ideas that the new presidenthas emphasisedin his approach to climate change.

Paris pledge

相反他predecessor’s decision to leave the Paris Agreement, at a “leaders summit” on Earth Day 2021 Joe Biden announced a newnationally determined contribution(NDC).

In it, the UScommitsto cutting greenhouse gas emissions 50-52% below 2005 levels by 2030.

This compares with theold targetfrom 2015, set by president Barack Obama, which was to cut greenhouse gas emissions by 26-28% by 2025 compared to 2005.

OFFICIAL

的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/PUSAoBNEV5pic.twitter.com/SqAmReb6K5

— Simon Evans (@DrSimEvans)April 22, 2021

的new target builds on aprevious pledgeby 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.

的NDC wasalso seen由评论家在作为一个重要举措courage 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 –describedthe US commitment as “critically insufficient” for achieving the Paris Agreement temperature goals.

While CATsaidBiden’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 metwith dismayby the international community, not least because of the enormous contribution the US makes – and has made – to global emissions.

的country’s annual greenhouse gas emissions were 6,534m tonnes of CO2 equivalent (MtCO2e) in 2015, according todatacompiled by the Potsdam Institute for Climate Impact Research (PIK).

的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 havefallen slightly, although not as rapidly as inprevious 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 fornearly twiceas many emissions as the closest contender, China, which today has a population four times larger than the US.

的nation’s per-capita emissions are also among the highest in the world and roughlythree timesthe global average.

的US ispart ofthe “Umbrella group” during theUnited Nations Framework Convention on Climate Change(UNFCCC) talks, alongside other developed nations including Australia, Japan and Canada.

It has had a volatile relationship with international climate diplomacy and hasoftenbeen accusedof undermining negotiations.

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 Bushmade it clearat 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.

This played out with theKyoto Protocolin 1997, which only required wealthy nations to cut their emissions and wassigned byBill Clinton’s administration.

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 rejectedthe protocol and the US has never subsequently ratified it. Subsequently, other nations either withdrew, in the caseof Canada, orfailed to renewtheir commitments after 2012.

Obama triedto pusha new agreement at COP15 in 2009, but theCopenhagen Accordthat emerged was not legally binding and the event waswidelyseenas a failure. The next major moment for a global deal came at COP21 in Paris six years later.

的resultingParis Agreementwas viewed as a diplomatic success and akey partof Obama’s climate legacy. Hedescribed itas “a tribute to American leadership”.

的US was seen as a key driver of acompromisethat 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 administrationmade it clearit intended to withdraw the US from the Paris Agreement. This decision did not comeinto effectuntil November 2020 and two months later Biden hadreversedit with another executive order.

In terms of its other international obligations, the US isregardedas having fallen short on its climate finance commitments to poorer nations. (The Trump administrationalso attemptedto withdraw funding from the UNFCCC itself.)

Under Obama, the US pledged $3bn to theGreen Climate Fund, buthad onlyhanded out $1bn before support was withdrawn under Trump. The Biden administration has now proposed spending $1.2bn in his 2022 budget.

According totheWorld 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 administrationannouncedits intention to double US international climate finance by 2024 and triple funding for adaptation,relative tothe $2.8bn a year committed during the second half of the Obama administration. The announcement doesnot mentionthe Green Climate Fund.

Climate policies and laws

由于困难通过气候法案a Congress divided along party lines, US federal climate efforts have beenproceedinglargely under theClean Air Act.

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 asMassachusetts vs EPAconcluded 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. Thishas since formedthe basis of the agency’s action to regulate emissions from vehicles and industrial facilities.

的Clean Power Plan, which wasdevelopedunder the Clean Air Act in 2015, marked a groundbreaking attempt to set limits on CO2 emissions from US power plants.

Originally setto beginin 2022, it was themain meansby which the Obama administration aimed to achieve its original NDC under the Paris Agreement.

However, the Trump administration attempted to repeal the plan and replace it with his far weakerAffordable Clean Energyrule. In early 2021, a federal appeals courtruledthat 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 CO2was estimatedto 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. (Ithas nowbeen returned to its Obama-era value.)

的re have been further efforts to pass more climate-relevant legislation, particularlysome formof acap-and-tradesystem in which limits are set on emissions and companies are able to buy and sell allowances if they need to exceed these limits.

Notable examplesincludesignificant 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 strongRepublican oppositionin the Senate andlobbyingby fossil fuel interests and was, ultimately, scrapped.

Similarly, oil-industry lobbyists have been implicated in holding backstate initiativesto try and introduce carbon pricing.

Despite these failures, there have been successful examples of regional cap-and-trade systems in the US.

的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’scap-and-trade programmeis 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 reacheconomy-wide carbon neutralityby 2045.

Over the years there have also been federal efforts to support clean energy, including the 2005Energy Policy Actand the 2007Energy 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).

的George W Bush administration authorised the creation of theAdvanced 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’srecovery actand areviewof its progress in 2017 found that it has been successful in driving innovation. Biden is now seeking to replicate this success with a newAdvanced Research Projects Agency-Climate(ARPA-C) initiative.

的Covid-19 pandemic has indirectly led to new climate policies, including theConsolidated Appropriations Actat 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 neverthelessincludedtax breaks for renewables, carbon capture and storage (CCS) initiatives and a phaseout of planet-warming hydrofluorocarbons (HFCs).

It was describedby somecampaignersas the “most significant” federal climate legislation ever passed in the US.

Since then, the Biden administrationhas proposedfurther 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.

的president said the plan would “lead to a transformational progress in our effort to tackle climate change with American jobs and American ingenuity”.

Renewables

Renewable energy from wood and some hydroelectric dams powered the US during its early industrialisationbefore beingsuperseded 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 2020andEmber Global Electricity Review 2021. Chart by Carbon Brief using Highcharts.

的USranks secondin the world for renewable power, with 311 gigawatts (GW) of capacity as of 2020, according to theInternational Renewable Energy Agency(IRENA). This is about twice as much as Brazil, in third place, but only around a third of China’s capacity.

Wind and solar generation have been growing rapidly,doublingin just five years to produce 12% of US electricity in 2020, according to analysis by climate thinktankEmber.

Together with other renewables,they overtookcoal power last year for the first time, with 21% of the electricity mix.

的se technologies have beenlargely shelteredfrom 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 totheEnergy Information Administration(EIA).

风现在renewab的全国最大的来源le power, surpassing hydro in 2019. The US remains the world’s third largest hydropower producer by capacity, after China and Brazil, according to theInternational Hydropower Association.

A亚慱官网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, areconcentrateddown the middle of the nation where wind speeds are highest.

Biden has pledged to achieve “100% carbon-free electricity by 2035”. Recent analysissuggestsemissions 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 Ricohave legislatively committedto 100% clean electricity by 2050 or earlier, while another eight states have a non-binding 100% goal.

Net-zero targets for 2050have alsobeen set by some of the nation’s biggest utilities.

(Asone papernotes, the US will need to do more than decarbonise electricity to achieve its climate targets. The nation’s building stock, for example, isconsiderably lessenergy efficient than other wealthy nations.)

的re has been some federal support for renewables (See: Climate policies and laws), notablytax incentives, such as the renewable electricity production tax credit (PTC) and the investment tax credit (ITC), which have played asignificant rolein expanding wind and solar.

However, state-level policies have also been important.Renewable portfolio standardsthat require electricity suppliers to provide a certain amount of renewable power havebeen importantin the proliferation of these technologies.

So far,29 statesand Washington DC have one in place, including Republican-dominated states such as Texas. (In fact, Texashas morewind, 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 stateshad EERS in place.

Nuclear

的US is the world’s largest producer of nuclear power, accounting for more than 30% of worldwide nuclear generation of electricity, according to theWorld Nuclear Association.

Nuclear is also the largest single source of clean power in the US, with 19.5% of generation,according toEmber.

的nation wasa pioneerin early nuclear development, with the first commercial nuclear plant built at Shippingport, Pennsylvania, in the late 1950s.

A major setback came in 1979 with theThree Mile Island accident. Following the incident, nuclear plant construction in the USslowed dramaticallyin the face of new safety standards.

的re was talk of a “nuclear renaissance” during the 2000s,spurred onby financial incentives in the government’s Energy Policy Act of 2005.

In 2012, thefirstnuclear power reactors for decades were approved at the existing Vogtle nuclear power plant in Georgia. Theseremainthe only new reactors under construction, as plans for an additional pair of reactors in South Carolinawere abandonedin 2017.

Since then the fracking boom (See: Oil and gas) and resulting low gas priceshave discouragedthe construction of new nuclear capacity.

As亚慱官网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 stateshave consideredexpanding their renewable portfolio standards to include other low-carbon sources of power. New York introduced a “zero-emissions credit” system to itsclean energy standardspecificallyto subsidiseits nuclear plants.

Under Trump, the government’s Office of Nuclear Energystatedit was “committed to reviving and revitalising the nuclear industry” and that the administration was “all in” on the technology.

In arare momentof bipartisan agreement, the presidentsignedbills to support the development of advanced nuclear technology in a bid to keep existing reactors online.

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 – isexpectedto shut down. Themost recentretirement was Indian Point, about 25 miles north of New York City, which previously provided a quarter of the city’s power.

Energy experts haveexpressedconcerns about the impact the shrinking US nuclear fleet could have on the nation’s emissions.

Analysis by theEIAandotherssuggests that when US nuclear plants have been retired in recent years they have been replaced by fossil fuels. However, othershave arguedthat retiring nuclear capacity saves money that can then be investedin renewables.

In 2019, the thinktank Rhodium Groupstatedthat 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-19had putfurther pressure on nuclear plants due to their high operating costs.

的Biden administration’s policy on nuclear power isessentiallya continuation of Trump’s, albeit framed around tackling climate change rather than energy security. The president’splatformmentions using ARPA-C to develop advanced nuclear reactors “that are smaller, safer and more efficient at half the construction cost of today’s reactors”.

Coal

As of January 2021, the US had 234GW ofoperating coal plants, the world’s second largest fleet and about 11% of the global total, according to theGlobal Coal Plant Tracker. This is around a quarter the size of China’s capacity.

According toyabo亚博体育app下载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.

的country is also thethird largestproducer of coal and has the world’slargest reserves, with around a quarter of the global total, according to BP.

Five statesaccount for about 71% of total US coal production, with Wyoming alone responsible for 39%.

Coalwasa 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. (Aroundtwo-thirdsof 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 bothroughly halvedover the past decade. There are currently no new coal plants in the pipeline and the chances of any emerging are seen asunlikely.

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.

的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.

的nation does not have a phaseout date for coal power, but the pace ofplant decommissioninghas sped up inrecent years具有126兆瓦容量的退休在2000 - 2020之间. 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 toGlobal 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 spiralhas continuedregardless.

Mining companies, includingbig namessuch as Peabody Energy and Westmoreland,have signalledthat they expect demand to continue falling amidsuccessivewaves ofcoal company bankruptcies.

Despite Trump’srollbackof the Clean Power Plan, utilitiesstill saidthey intended to go ahead with coal closures and while thermal coal exports hitrecord highsduring his presidency – mainly due to Asian demand – there is evidence this market is alsoweakening.

During the firstpresidential debatelast 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 simplyno longerthe cheapest way to generate electricity as the price of gas (see: Oil and gas) and renewables declines.

This has beenparticularly evidentduring the pandemic, as in many regions coal plants aremore expensiveto operate so were the first to be shut off when demand dropped.

Environmental regulations have also had an impact. A recent study found theCross 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 Standardshave alsoreportedlyimpacted coal generation.

的same paper also concluded that environmental campaigning played a considerable role, notably Sierra Club’sBeyond Coalcampaign which has made use of lawsuits targeted at individual power plants.

Coal use stillvaries a lotbetween states, with West Virginia getting nearly all of its power from burning the fossil fuel and Californiavirtually none.

State-level politics also impacts the speed of shutdowns, with theLos Angeles Timesreporting 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 byregulated utilities, there is evidence that they are running in some energy markets even when they are losing money, with costs beingpassed ontocustomers.

Oil and gas

的US is the world’s top producer and consumer of both oil and fossil gas, according to thelatest figuresfrom 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 andforeign policyfor decades.

的“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 widelybeen viewedas 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 responseto 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.

Starting in 2005for gasand 2008for oil, these innovations saw production rise rapidly, with the US overtaking other big producers, such as Russia and Saudi Arabia, within a decade.

Gas has helped tobring downUS emissions as it has edged out coal in the power sector. However, many expertsand campaignershave raised concerns about replacing one fossil fuel with another. (Researchhas also suggested that the impact of fracking on cutting emissions may have beenoverstated.)

的US shale gas boom has alsobeen linkedto a spike in the potent greenhouse gas methane – which leaks from operations – in the planet’s atmosphere.

的EPA under Obamaproducedits 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 wasopposed, even by some oil and gas companies.

Biden has sincecommitted美国再一次解决甲烷。的Obama administration pledged to cut methane emissions by 45% below 2012 levels by 2025 and the new EPA administrator Michael Regan hassuggestedBiden’s target could exceed that.

的US is home to two of the world’s largest oil and gas companies, ExxonMobil and Chevron,neitherof which have committed to tackling climate change to the extent of their European counterparts.

For decades, the fossil fuel industry in the US haspushed backagainst climate science and lobbied against measures to limit emissions (see:Climate policies and laws).

Nevertheless, industry group theAmerican Petroleum Institutehas recentlythrown its weightbehind carbon pricing andmethane regulationsin an apparent bid to align with the Biden administration.

石油和天然气的活动在美国一直是the targets of environmental campaigners. Major pipelines, such as Dakota Access and Keystone XL,have facedconsistent 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 subjectof dozensof attempts by Congress to allow drilling for oil, culminating in success under the Trump administration.

Upon becoming president, Bidensignedan 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 anendto finance for fossil fuels overseas.

However, despitepressure fromfellow Democrats as well asclaims madeby 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.

Akey argumentfrom 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 amajor exporterof fossil fuels and in 2021 its exports of liquefied natural gas (LNG) to major markets in China, Japan and South Koreareachedrecord levels.One studyfound 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.

Transport

Transport produces the largest share of US greenhouse gas emissions, ataround 28%, according to the EPA. The nation is alsothe largestcontributor to transport emissions in the world.

Cars, vans and small trucksmake upthe most significant chunk of these emissions, at 59%, and larger trucks and lorries make up 23%.

飞机占运输排放和whi的9%le the EPA finalised itsfirst-everaviation emissions rules last yearit is notprojecting any emission reductions as the modifications to planes it calls for would have happened anyway.

Driving is often viewed as fundamental toAmerican cultureand there are1.2 motor vehiclesper licensed driver in the country.

的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 beenrecognisedas playing a critical role in advancing the electric vehicles industry.

Based on data from theEV-Volumesdatabase for 2020 and theInternational Energy Agencyfor previous years, the US is home to around 17% of the 10.4m electric vehicles on the road. As of 2019,more thanhalf the world’s 11,200 hydrogenfuel cell carswere located in California.

Billions of dollars in Biden’s Covid-19stimulus planshave been set aside to promote electric vehicles but also to improve bus and rail networks. As it stands, the nation’s public transport infrastructure iswidelyrecognisedas being less effective than its European and Asian counterparts.

US vehiclestend to belarger, 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 studyfound that fuel savings in cars and other “light duty” vehicles have saved 17bn tonnes of CO2 (GtCO2) over the past 45 years.

的corporate average fuel economy(CAFE) standard, set in miles per gallon, was established by theNational 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 theMassachusetts vs EPASupreme Court ruling in 2007, the EPA was able to begin setting standards for grammes of CO2 emitted per mile.

In 2010, the Obama administrationoversawthe 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 industrywhile stipulatingthat companies had to invest in improving vehicle efficiency.

的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 previouslyactively lobbiedagainst this ability.)

In 2012, the governmentissuedits second set of rules that required automakers to nearly double the average fuel economy of new cars and trucks by 2025, measures itsaidwould cut emissions from cars and light trucks in half over this period.

However, when the Trump administration took over itannouncedplans to roll back regulations, freezing standards at 2020 levels and stopping California from setting its own standards.

States and some motor companiesopposedthis effort. Studies suggested it wouldlead toconsiderable extra emissions and that it was based on “flawed” economic analysis.

Since taking power, Biden hasordered agenciesto revisit this decision alongside other environmental rollbacks brought in by the last administration.

Earlier this year, Californiaannouncedthat itwill requireall new cars and trucks sold in the state to be zero-emissions by 2035, a movethat couldcut the state’s emissions by 35%. Washington statemay goeven further with a 2030 target.

Another key policy for transport emissions is theRenewable 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.

的standard also had a secondary goal of cutting emissions.

However, according to the USGovernment Accountability Officeit has had “little effect”, largelybecauseadvanced biofuels that cut emissions more effectively are not being used in line with expectations.

Agriculture and forests

的US isthe largest exporterof agricultural products globally, shipping 20% of its produce abroad. Food and related industriesmake upa 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 andaround 10.5%of total US greenhouse gases come from agriculture, according to government figures.

At more than 12m tonnes in 2018, the US is theworld’s largestbeef producer and livestock accounts formore than 40%of its agricultural emissions –predominantly methane.

Roughlyhalfof agricultural emissions are related to use of synthetic fertilisers and manure, whichemit nitrous oxide.

Besides making a significant contribution to climate change, US agriculture isalso expectedto 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 cornis produced in the US than in the whole of Asia.

Much ofthe 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 periodof growthethanol production has slowed down in recent years. The agricultural industryhasattributedthis 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 itsAgriculture 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”.

的agenda included a focus on carbon sequestration through tree planting, a climate strategy that has beenwelcomedeven by otherwisesceptical Republicans.

This included Trump himself, who supported aTrillion Trees Actand evensignedan executive order to form a council that would coordinate tree-planting efforts.

According to theFAO, 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 therehas beenextensive 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 2019reportby theNatural 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.

WRIyabo亚博体育app下载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

的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.

的annual mean temperature of the contiguous US – all the states, excluding Alaska and Hawaii – hasalready risenby around 1.2C since the period of 1895-1915.

的USNational 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.”

Scientistshave linkedthe record-breaking rain that struck Texas in 2017 during Hurricane Harvey and the wildfires thathave ragedacross California to climate change.

More events including heatwaves, flooding and storms that have been influenced by climate change can be seen in this亚慱官网map.

One measure of the increasing severity of these impacts is the rate of so-called “billion dollar disasters” relating to climate and weather.

的National Oceanic and Atmospheric Administration(NOAA)concludedthere were 22 such events – a new record – in 2020 and that the number and cost of these disasters has been increasing.

Climate change is expected to drive migration both from outside the US and within it, and there isevidencethis isalreadytaking place due to droughts and sea level rise.

In 2016, residents of an indigenous Inupiat villagevotedto relocate their community from an island in Alaska that had been vanishing due to erosion and flooding. A similar situation in Louisiana hasseencoastal “refugees” relocated as their homes are inundated with water.

的Pentagon hasidentifiedclimate change as a national security priority and a 2019reportby the Department of Defense examined the impact of climate change on military activities. (The department itself has an emissions footprintcomparable witha medium-sized country.)

的threats that the military has highlighted includedesertificationdestabilising societies and melting iceopening upnew routes to the US through the Arctic.

In 2013, during the Obama administration, the president signed anexecutive ordercalling on every federal agency to release a climate change adaptation plan. The EPA published aplanin response to this request, as did other key agencies, such as thetransport,defenceandenergydepartments.

As捕获by the Georgetown Climate Centre, many state and local governments have also released their own climate adaptation plans, particularly those in coastal regions.

的“resilience council” that emerged from Obama’s executive order issuedguidanceto 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 hiscampaign promiseto “define the climate adaptation agenda”.