By Josh Gabbatiss

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. REGlobal presents excerpts…

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. Climate change is a highly divisive issue in US politics and comprehensive government action has routinely been blocked by members of the Republican Party. 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.

Infographic by Joe Goodman


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

As part of the US Climate Alliance, a bipartisan coalition of state governors, 25 states and Washington DC have set climate targets to “advance the goals” of the Paris Agreement.

Fossil fuel companies are known to lobby US politicians extensively and have been accused of exerting considerable influence over the nation’s climate policy.

Central to the green new deal is the concept of environmental justice and a “just transition” for fossil fuel workers, ideas that the new president has emphasised in his approach to climate change.

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 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.

Paris pledge

Having reversed his predecessor’s decision to leave the Paris Agreement, at a “leaders summit” on Earth Day 2021 Joe Biden announced a new nationally determined contribution (NDC).

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.

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)
New version of the chart by Simon Evans

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. It has had a volatile relationship with international climate diplomacy and has often been accused of 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 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. This played out with the Kyoto Protocol in 1997, which only required wealthy nations to cut their emissions and was signed by Bill 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 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 resulting Paris Agreement was viewed as a diplomatic success and a key part of Obama’s climate legacy. He described it as “a tribute to American leadership”. 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

Due to difficulties passing climate legislation in a Congress divided along party lines, US federal climate efforts have been proceeding largely under the Clean 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 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.

The Clean Power Plan, which was developed under the Clean Air Act in 2015, marked a groundbreaking attempt to set limits on CO2 emissions from US power plants. Originally set to begin in 2022, it was the main means by 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 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). It was described by some campaigners as the “most significant” federal climate legislation ever passed in the US.

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.

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

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.

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.”

Scientists have linked the record-breaking rain that struck Texas in 2017 during Hurricane Harvey and the wildfires that have raged across California to climate change.

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. The National Oceanic and Atmospheric Administration (NOAA) concluded there 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 is evidence this is already taking place due to droughts and sea level rise.

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.)

The threats that the military has highlighted include desertification destabilising societies and melting ice opening up new routes to the US through the Arctic.

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”.

The article has been sourced from Carbon Brief and can be accessed by clicking here.