In Paris in 2015, almost 200 countries signed a landmark agreement designed to avoid the worst consequences of climate change.
But despite some progress in areas like renewable energy, the world has continued to warm at a rapid pace. The Paris agreement is at the heart of the international commitment to tackle rising global temperatures.
It came into force on 4 November 2016 and saw almost all the nations of the world agree to cut the greenhouse gas emissions which cause global warming.
However, the United States – the world’s second biggest greenhouse gas emitter -withdrew from the deal in January 2026 under President Donald Trump.
The US also withdrew during Trump’s first presidency, but it rejoined in 2021 under his successor President Joe Biden.
The only other UN member states outside the Paris agreement are Iran, Libya and Yemen.
The Paris agreement lists a series of commitments:
to “pursue efforts” to limit global temperature rises to 1.5C, and to keep them “well below” 2.0C above those recorded in pre-industrial times, generally considered to mean the late 19th Century to achieve a balance – known as net zero – between the greenhouse gases that humans put into the atmosphere and the gases that they actively remove, in the second half of this century each country to set its own emission-reduction targets, reviewed every five years to raise ambitions richer countries to help poorer nations by providing funding, known as climate finance, to adapt to climate change and switch to renewable energy
The 1.5C target is generally accepted to refer to a 20-year average, rather than a single year.
So, while 2024 was more than 1.5C warmer than pre-industrial times, it did not mean the Paris agreement threshold has been breached.
Every 0.1C of warming brings with it greater risks for the planet, such as longer heatwaves, more intense storms and wildfires, according to climate scientists.
But a very large body of scientific evidence shows that warming of 2C or more would bring far greater impacts, on top of those felt at 1.5C, UN scientists say.
These include: more people being exposed to extreme heat, higher sea levels as glaciers and ice-sheets melt, increased risks to food security in some regions due to more extreme weather, greater chances of some climate-sensitive diseases spreading, such as dengue, more species being threatened with extinction and the loss of virtually all coral reefs.
Some changes could become irreversible if so-called “tipping points” are crossed.
It is not clear exactly where these sit, but once these thresholds are passed, changes could accelerate and become irreversible.
The Paris deal restated a 2009 commitment that richer countries should provide $100bn (around £73bn) annually by 2020, to help developing nations deal with the effects of climate change, and build greener economies.
Although only $83.3bn was raised in 2020 itself, data from the OECD shows the goal was eventually achieved in 2022.
In 2023, countries agreed for the first time that a fund should be established exclusively for loss and damage. This is money to help countries recover from the impacts of climate change.
At COP29 in 2024, richer nations committed to providing $300bn (around £219bn) a year to developing nations by 2035. Developing countries – which had hoped for more – criticised the “paltry sum”.
World leaders meet every year to discuss their climate commitments at international summits known as COPs (Conference of the Parties). All COPs since 2015 have tracked how countries are building on what they promised in Paris.
At COP28 in 2023, countries agreed for the first time to “contribute” to “transitioning away from fossil fuels”, although they were not forced to take any specific action.
Countries also agreed to treble the global capacity of renewables – such as wind and solar – by 2030.
But the most recent summit, COP30 in 2025, failed to directly mention fossil fuels in the final deal.
(BBC)
