Global Carbon Budget
” As far as the future is concerned, it is not a question of predicting it, but of making it possible “
– Antoine de Saint Exupéry, Citadelle, 1948
Where does this figure come from?
UPDATE: In October 2018 the Special report on 1.5 degrees was published by the IPCC
From the summary for policy makers:
"C.1.3. Limiting global warming requires limiting the total cumulative global anthropogenic emissions of CO2 since the pre-industrial period, that is, staying within a total carbon budget (high confidence).14
By the end of 2017, anthropogenic CO2 emissions since the pre-industrial period are estimated to have reduced the total carbon budget for 1.5°C by approximately 2200 ± 320 GtCO2 (medium confidence). The associated remaining budget is being depleted by current emissions of 42 ± 3 GtCO2 per year (high confidence). The choice of the measure of global temperature affects the estimated remaining carbon budget. Using global mean surface air temperature, as in AR5, gives an estimate of the remaining carbon budget of 580 GtCO2 for a 50% probability of limiting warming to 1.5°C, and 420 GtCO2 for a 66% probability (medium confidence).15 Alternatively, using GMST gives estimates of 770 and 570 GtCO2, for 50% and 66% probabilities,16 respectively (medium confidence). Uncertainties in the size of these estimated remaining carbon budgets are substantial and depend on several factors. Uncertainties in the climate response to CO2 and non-CO2 emissions contribute ±400 GtCO2 and the level of historic warming contributes ±250 GtCO2 (medium confidence). Potential additional carbon release from future permafrost thawing and methane release from wetlands would reduce budgets by up to 100 GtCO2 over the course of this century and more thereafter (medium confidence). In addition, the level of non-CO2 mitigation in the future could alter the remaining carbon budget by 250 GtCO2 in either direction (medium confidence). " 14. There is a clear scientific basis for a total carbon budget consistent with limiting global warming to 1.5°C. However, neither this total carbon budget nor the fraction of this budget taken up by past emissions were assessed in this Report. 15. Irrespective of the measure of global temperature used, updated understanding and further advances in methods have led to an increase in the estimated remaining carbon budget of about 300 GtCO2 compared to AR5. (medium confidence) {2.2.2} 16. These estimates use observed GMST to 2006–2015 and estimate future temperature changes using near surface air temperatures |
We have (optimistically) used the larger 570 GT CO2 figure for the remaining budget from the end of 2017 for a 66% chance of staying below 1.5°C . We've then backdated it to when we started the calculator in 2016 by adding the global emissions between 2016 and 2018. Giving us each 89 tonnes CO2 per person.
2016 is an arbritary cut off date for beginning to share the budget equally. However, having set a date within this calculator for sharing equally, it would become less equitable to move that date forward as time progresses. Taken to the extreme, we could continue with our current emissions untill there is no budget left and then share the (empty) budget.
It's worth bearing in mind that in the UK we don't really have a carbon budget, we have a carbon debt to the rest of the world (of about 500 Tonnes CO2 per person). In the UK we used up our per capita share of the 1.5 degree C global carbon budget. Between 1969 and 2016 (the date we are proposing to start dividing the remaining budget equally), we have used about 500 tonnes CO2 each in the UK. So the 89 tonne CO2 budget we are working to here is like the bit of money you might borrow to put in the bank to try and make a start with paying off your debts . It sort of doesn't really exist but we're pretending it does so we can get to zero from where we're at without throwing up our arms in despair. Just so you know.
2016 is an arbritary cut off date for beginning to share the budget equally. However, having set a date within this calculator for sharing equally, it would become less equitable to move that date forward as time progresses. Taken to the extreme, we could continue with our current emissions untill there is no budget left and then share the (empty) budget.
It's worth bearing in mind that in the UK we don't really have a carbon budget, we have a carbon debt to the rest of the world (of about 500 Tonnes CO2 per person). In the UK we used up our per capita share of the 1.5 degree C global carbon budget. Between 1969 and 2016 (the date we are proposing to start dividing the remaining budget equally), we have used about 500 tonnes CO2 each in the UK. So the 89 tonne CO2 budget we are working to here is like the bit of money you might borrow to put in the bank to try and make a start with paying off your debts . It sort of doesn't really exist but we're pretending it does so we can get to zero from where we're at without throwing up our arms in despair. Just so you know.
Outdated: from 2016
For a 66% chance of staying below 1.5˚C we have 400 GtCO2 left to emit from 2011
For a 66% chance of staying below 2˚C we have 1,000 GtCO2 left to emit from 2011 |
A Gt of CO2 is a billion tonnes (1,000,000,000 tonnes)
A 66% chance is two bullets in a six bullet gun in a game of Russian roulette. I'm not sure these are good odds of staying safe.
A 66% chance is two bullets in a six bullet gun in a game of Russian roulette. I'm not sure these are good odds of staying safe.
The global temperature has already risen by about 1˚C compared to pre-industrial levels. And there is some evidence that the amount of CO2 now in the atmosphere will lead to over 1.5˚C temperature rise over the next few centuries even if we stopped all emissions immediately. But, being hopeful and assuming we still have a chance to stay below 1.5˚C, continuing:
A 2˚C rise in temperature is considered by the IPCC to be the threshold between relatively “safe” and dangerous warming. A chance of 66% is a 2/3 chance of staying “safe”.
Many climate scientists think this is a dangerously high and unsafe target and we should aim to stay below 1.5˚C (e.g. James Hanson).
Bill McKibben at 350.org are asking for a budget of 565 Gt CO2 from 2012. Island nations are desperate for a 1.5˚C target in order to continue to exist.
So we could aim to release less than 400 Gt CO2 to stay below 1.5˚C and make sure we definitely emit less than 1,000 Gt CO2 to stay below 2˚C.But it is already the end of 2015 We have already used an estimated 158 Gt CO2 between 2011 and 2015 . See www.globalcarbonproject.org for details (fossil fuel and land use emissions 2012-2015.
So for a 66% chance of staying below 1.5˚C we have 400 - 158 = 242 Gt CO2 left to emit
For a 66% chance of staying below 2˚C we have 1,000 - 158 = 842 Gt CO2 left to emit
A 2˚C rise in temperature is considered by the IPCC to be the threshold between relatively “safe” and dangerous warming. A chance of 66% is a 2/3 chance of staying “safe”.
Many climate scientists think this is a dangerously high and unsafe target and we should aim to stay below 1.5˚C (e.g. James Hanson).
Bill McKibben at 350.org are asking for a budget of 565 Gt CO2 from 2012. Island nations are desperate for a 1.5˚C target in order to continue to exist.
So we could aim to release less than 400 Gt CO2 to stay below 1.5˚C and make sure we definitely emit less than 1,000 Gt CO2 to stay below 2˚C.But it is already the end of 2015 We have already used an estimated 158 Gt CO2 between 2011 and 2015 . See www.globalcarbonproject.org for details (fossil fuel and land use emissions 2012-2015.
So for a 66% chance of staying below 1.5˚C we have 400 - 158 = 242 Gt CO2 left to emit
For a 66% chance of staying below 2˚C we have 1,000 - 158 = 842 Gt CO2 left to emit