Cop

Cop26 will be the 26th conference of the parties to the UN framework convention on climate change, the parent treaty to the 2015 Paris agreement. More than 120 world leaders are expected to attend, with more than 25,000 delegates from 197 countries, in the biggest diplomatic event on British soil since the second world war.

UNFCCC

The UN framework convention on climate change, signed in 1992 at the Rio Earth summit, binds all of the world’s nations – bar a handful of failed states – to “avoid dangerous climate change”. However, it did not set out in detail how to do so.

Kyoto protocol

The first attempt to turn the UNFCCC’s resolution into action was the 1997 Kyoto protocol, which set targets on emissions cuts for each developed country, stipulating a 5% cut in global greenhouse gases overall by 2012. Developing countries, including China, were allowed to increase their emissions. But the protocol immediately ran into trouble when the US, which signed the treaty under Bill Clinton, could not ratify it owing to opposition in Congress. The protocol eventually came into force without US backing, in 2005, but by then was largely irrelevant, so countries set out on the long journey to a new treaty that would fulfil the UNFCCC aims, resulting eventually in the 2015 Paris accord.

The Paris agreement

Forged at a landmark summit in December 2015, this marked the first time that both developed and developing countries agreed to limit greenhouse gases in order to stay within set temperature limits. The main goal of the Paris agreement is to limit global heating to “well below” 2C above pre-industrial levels, while “pursuing efforts” to stay within the lower, safer threshold of 1.5C. Countries set out targets to stay within those limits, in the form of nationally determined contributions (NDCs).

NDCs

Nationally determined contributions are national plans containing targets on emissions cuts, usually pegged to 2030, and some details on how they will be met. They form the heart of the Paris agreement. In the negotiations leading up to the Paris summit, countries were reluctant to accept “top-down” targets like those contained in the Kyoto protocol, which set a global goal for emissions reduction then divided up the cuts needed among the developed countries. Instead, they opted for each government offering the emissions reductions it thought feasible. However, this resulted in a set of NDCs submitted at Paris that would result in catastrophic heating, of more than 3C. So the Paris agreement contains a “ratchet” mechanism by which every five years countries must return to the negotiating table with fresh commitments, to bring emissions in line with the overarching temperature targets.

1.5C

The Paris agreement contains two key goals, of limiting global heating to “well below” 2C, while “pursuing efforts” to limit temperature rises to 1.5C above pre-industrial levels. These temperature goals have their roots in IPCC reports. The 2007 IPCC fourth assessment report suggested the world was likely to warm by at least 1.8C even if measures were taken to limit emissions, and by 4C if emissions went untrammelled. Keeping warming to about 2C was regarded as the outer limit of safety, beyond which the impacts of climate change – heatwaves, droughts, floods, sea level rises, fiercer storms and other extreme weather – would become catastrophic and irreversible. Some big emitters, including China, argued 2C was the only realistic limit and opting for a lower goal would be economically difficult. However, small island states pointed to science showing they were likely to be inundated, by sea level rises and storm surges, at warming above 1.5C. The conflict was eventually resolved in the compromise of two goals at Paris. A further IPCC report in 2018 found extreme weather and severe impacts from even a 1.5C rise, so for Cop26 the UK hosts made “keeping 1.5C alive” the core aim of the conference.

Net zero

This basically means reducing greenhouse gas emissions as far as possible and then offsetting any remaining irreducible emissions – for instance, from industrial processes that emit carbon dioxide, or sectors such as aviation where alternative technologies are not available – by fostering carbon sinks, such as forests. The concept has come under attack from campaigners who argue that some companies and governments are using net zero as a fig leaf by assuming they can offset emissions rather than reducing them.

Mitigation

Within the context of the UNFCCC, mitigation always means the reduction of greenhouse gas emissions.

Adaptation

(Also sometimes known as resilience.) The world has already warmed by 1.1-1.2C above pre-industrial levels, and some of the impacts of the current heating are irreversible, so even if we succeed in cutting emissions drastically, we will still need to adapt to the impacts of more extreme weather. Infrastructure, including transport, telecommunications networks, housing and rural areas will need to be adapted and protected, for instance by building railways less likely to buckle in the heat or roads less likely to melt, and building houses that will not overheat.

IPCC

The Intergovernmental Panel on Climate Change. The body of the world’s leading climate scientists, first convened by the UN and the World Meteorological Organization in 1988, has produced five comprehensive assessment reports since, each increasing in certainty and reinforcing the message that the climate crisis, caused by human actions that increase the levels of carbon dioxide and other greenhouse gases in the atmosphere, is accelerating. The latest IPCC report, the sixth, is part-way through publication: the first instalment, on the physical science of climate change, came out in August, delivering the starkest warning yet of the calamity we face. It found that the claimte crisis was “unequivocally” the result of human actions, was putting in train changes that in some cases were already “irreversible”, and that some of those changes were “unprecedented” in hundreds of thousands of years. The IPCC has been criticised for giving too conservative a view of climate science – its key findings, in the “summary for policymakers”, are subject to approval and amendment by governments before publication, which some say means they are unduly weakened.

Methane

A powerful greenhouse gas, which can trap heat in the atmosphere about 80 times more effectively than carbon dioxide. Whereas carbon dioxide lingers in the atmosphere for about a century once released, methane degrades in a couple of decades to carbon dioxide. It comes from leaking fossil fuel infrastructure, such as oilwells and shale gas wells, and from animal husbandry and other agriculture.

SLCPs

Short-lived climate pollutants. These are compounds such as methane, hydrofluorocarbons and soot. They degrade or fall out of the atmosphere more quickly than carbon dioxide, but while they are active can play a major role in heating the atmosphere, so actions to reduce them could buy humanity some time in cutting warming sooner. Methane, for instance, traps heat about 80 times more effectively than CO2, and moves to drastically reduce it could reduce warming by as much as 0.2Caccording to some estimates. Soot stains white snow and ice, and the dark surfaces absorb more heat, in a feedback loop. Hydrofluorocarbons are substitutes for the ozone-destroying chlorofluorocarbons, but they have a high warming potential, with some capable of trapping more than 11,000 times as much heat as CO2.

Carbon offsetting

Carbon dioxide has the same impact on the climate no matter where it is emitted and what the source, so if a tonne of carbon dioxide can be absorbed from the atmosphere in one part of the world it should cancel out a tonne of the gas emitted in another. So, in theory, companies, governments and individuals can cancel out the impact of some of their emissions by investing in projects that reduce or store carbon – forest preservation and tree planting are among them, but carbon credits are also awarded for projects that reduce fossil fuels in other ways, such as windfarms, solar cookstoves, or better farming methods. The practice has been controversial.

Article 6

One of the key areas still to be resolved at Cop26 is article 6 of the Paris agreement, which provides for the use of carbon markets. Countries are divided over the plans: there are concerns that some carbon credits are just “hot air” because they do not result in genuine emissions reductions; and concerns that under some proposals carbon credits could be counted twice. Some campaigners have called for article 6 and the carbon markets to be scrapped altogether. Brazil and other heavily forested nations have most interest in article 6 but disagreements over the issue overshadowed the last Cop, in Madrid in 2019, and the UK will be anxious to avoid a repeat.

Climate finance

Developing countries were promised, at the Copenhagen Cop in 2009, that they would receive at least $100bn a year in climate finance from 2020, from public and private sector sources, to help them cut greenhouse gas emissions and cope with the impacts of extreme weather. That promise was not met: OECD estimates, published in September, showed that climate finance in 2019 amounted to about $80bn, well short of the target.