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In signing the Paris Agreement, the world has committed preventing global average temperature from passing the thresholds of 1.5 to 2°C above pre-industrial averages, so as to avoid the most dangerous consequences of global warming. But how far away are these thresholds? And what do we need to do to change direction? The Climate Clock acts a public line in the sand and says, this is the date. It is a measuring stick by which we can evaluate our progress.

The Climate Clock is based on the best available science, and is updated each year to reflect the latest data by a team of leading climate scientists from around the world. Each year, we are able to show how we are doing in relation to 1.5 and 2°C. Have we gained time or lost time?

Humanity has the power to add time to the Clock, but only if we work collectively and measure our progress against defined targets.


The Climate Clock answers the question: given the current rate of emissions and level of human-induced warming, and assuming the emissions trend over the past five years continues into the future, how long will it be before the remaining allowable emissions for 1.5°C are used up?

1) Tonnes of CO2 Emitted
This value shows the total accumulated CO2 emissions from fossil fuel burning, cement manufacture and deforestation since 1870, based on the most recent data from the Global Carbon Project.

2) Global Warming to Date
This number represents the human contribution to observed global temperature increase. This Global Warming Index represents the portion of observed temperature change that can be attributed to all human drivers of climate change. We use 1850-1900 as the reference temperature for the “pre-industrial” period. This is the earliest period for which we have reliable measurements of global temperature, and is the most common reference period for pre-industrial temperatures used in scientific analyses and policy discussions.

3) Time left to 1.5
The time remaining until we reach +1.5°C above pre-industrial temperature is estimated based on extrapolating the most recent 5-year trend of global annual fossil fuel CO2 emissions and calculating the time until we emit the remaining carbon budget – i.e. the total allowable future emissions required to limit warming to 1.5°C. Fossil fuel emissions increased by about 1% (or 0.3 billion tonnes) per year between 2016 and 2019, and then decreased by 7% in 2020 as a result of COVID-19 lockdowns around the world. We assume fossil fuel CO2 emissions follow this past 5-years trend, while additional CO2 emissions from deforestation remain constant at current levels. We use the best estimate of the remaining carbon budget from the IPCC Special Report on 1.5°C, which for the 1.5°C temperature target corresponds to 500 billion tonnes from 2020 onwards.


Sixth Update March 27, 2021
1.5°C date: February 1, 2033

Fifth Update December 12, 2019
1.5°C date: November 11, 2032

Fourth Update December 5, 2018
2°C date: August 2, 2052
1.5°C date: December 1, 2034

Third Update November 2017
2°C date: November 14, 2045
1.5°C date: April 26, 2033

Second Update April 2017
2°C date: May 25, 2046
1.5°C date: August 25, 2033

First Update April 2016
2°C date: December 16, 2044
1.5°C date: July 26, 2032

Clock Launch November 2015
2°C date: December 17, 2043




“We have been given a very short window of opportunity by the Intergovernmental Panel on Climate Change (IPCC) — that’s why the Climate Clock is so important. The clock is ticking and we need to be reminded of how little time we have left to act.” — David Suzuki


The Climate Clock
Tracking Global Warming in Real Time

Global warming to date

Time left to +1.5ºC

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Tonnes of CO2 Emitted