Sunday, August 21, 2016

These Charts Show What the Paris Climate Agreement Is Up Against

Maximum number of years of CO2 emissions release (Credit: Mercator Research Institute) Click to Enlarge.
There has been a heated debate over the last few years about if and how we can prevent the world from warming more than 2 degrees Celsius.  At the Paris climate conference last year, countries set out an even more ambitious goal — keeping the world under 1.5C of warming.  We know relatively little about the benefits, risks and challenges associated with reaching the 1.5C target, but our knowledge in the area is expanding rapidly.  The Intergovernmental Panel on Climate Change is now tasked with mapping out the state of the scientific knowledge on the 1.5C goal in a report due in the autumn of 2018 that is expected to inform future international negotiations. ...

The 1.5C goal is elusive
There are many open scientific questions around the costs and benefits of keeping global warming below 2C versus 1.5C that will need to be addressed by this special report.  Whether we can feasibly reach 1.5C — and how — will be the most important.

Many experts see a growing dissonance between the increasing ambitions of climate policy and the lack of success in achieving sustained emission reductions today.  So far, there is no track record for reducing emissions globally. Instead, greenhouse gas emissions have been rising at a faster pace during the last decade than previously — despite growing awareness and political action across the globe.

co2 emissions allowance
The remaining net amount of CO2 that can still be released to the atmosphere in order to keep temperatures rise below 1.5C is close to zero.  Even in the most optimistic case, it will not take longer than five years to exhaust the remaining carbon budget at current rates of CO2 emissions.  It will be, on the other hand, about 10-25 years before the world crosses the budget line for 2C.

So is reaching 1.5C goal still thinkable?  The initial evidence in the last IPCC report points towards the (theoretical) existence of emission reduction pathways consistent with the 1.5C goal, but the technological, economic and institutional requirements are enormous.  Take all of the most difficult features of individual pathways to 2C — like fast and ambitious climate action in all countries of the world, the full availability of all required emissions reduction and carbon removal technologies, as well as aggressive energy demand reductions across the globe — the feasibility of which were so heatedly debated prior to Paris.  This gives you an idea of the challenge associated with the more ambitious 1.5C goal.

Keeping the temperature increase below 1.5C appears rather elusive — the institutional challenge in mobilizing adequate action at the timescales required appears too big.  Still, positive surprises, unexpected technological breakthroughs or rapidly changing attitudes and ambitions may well occur and keep the 1.5C goal within reach.

Annual CO2 Emissions Graph (Credit: Mercator Research Institute) Click to Enlarge.
What kind of technologies we would need to meet a 1.5C goal?  One prominent feature of 1.5C pathways is their fundamental dependence on the ability to remove large amounts of CO2 from the atmosphere through carbon dioxide removal technologies.  Such CO2 removals buy us time, while we are reducing emissions towards a fully decarbonized world economy — as with a bank loan, we overshoot our carbon budget in the short term and pay it back later, with interest.  All 1.5C pathways to date are characterized by such an overshoot.

Read more at These Charts Show What the Paris Climate Agreement Is Up Against

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