ADDING THE METRIC OF TIME TO THE GLOBAL WARMING CONVERSATION
In signing the Paris Agreement, the world has committed to preventing the 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 as 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 collected 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 NUMBERS ON THE CLOCK
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 C and 2 C
The time remaining until +1.5 C and +2 C date is estimated based on extrapolating the most recent five-year trend of global annual fossil fuel CO2 emissions and calculating the time until we emit the remaining carbon budget — the total allowable emissions for 1.5 and 2 C. Fossil fuel emissions are currently increasing by about 0.1 per cent (or 0.4 billion tonnes) per year and are expected to exceed 37 billion tonnes in 2018.
We assume CO2 emissions from deforestation remain constant at current levels. We use best estimates of the remaining carbon budget from the IPCC Special Report on 1.5 C: 770 billion tonnes after 2017 for 1.5 C and 1690 billion tonnes for 2 C. We use the IPCC budget estimates that are based on observational warming estimates to retain consistency with our estimate of global warming to date.
These estimates of the remaining carbon budget assume a 25 per cent warming contribution from non-CO2 greenhouse gas and aerosol emissions.
CLOCK UPDATE HISTORY
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