Report: Cutting Carbon Emissions Isn’t Necessarily At Odds With A Stronger World Economy (Updated)

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Work from an international effort to model climate change’s effects suggest that cutting more carbon emissions needn’t hold humanity back from a strong global economy over the next century. The report is part of the Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC), which was set up by the United Nations to offer a comprehensive assessment of climate science. The last report — the AR4 — was put out in 2007. And while the AR5 is not due until 2014, numbers from it are already making their way out.

One big change between the AR4 and the AR5 will be the switch from “Special Report On Emissions Scenarios” (SRES) to “Representative Concentration Pathways” (RCPs) as tools for projecting future climates and economies. Both are extremely involved models that build in greenhouse gas emissions, climate changes, population changes, technological development, land use, and a host of other factors. But the RCPs are more advanced, and more importantly they also model what would happen if governments got proactive about cutting carbon emissions through policy changes.

The graph below shows the concentration of carbon in the atmosphere in parts per million (ppm) under four different RCP scenarios. The RCP2.6 (the green line) features the most aggressive reduction in carbon emissions by the global community, which stabilizes the carbon concentration around 450 ppm and then slowly brings it down. The RCP8.5 (the blue line) shows us blasting nearly all the way to 1,000 ppm by 2100, which is what we’re likely to do if we continue business as usual.


CREDIT: The representative concentration pathways – van Vuuren 2011

Now look at this graph. That’s the wealth the planet will produce as modeled under the four RCPs.


CREDIT: The representative concentration pathways – van Vuuren 2011

It’s important to note that the RCPs are drawn from separate models, which means the baseline assumptions they started with for GDP growth aren’t directly comparable. Essentially, the starting line for the global economy before carbon reductions are factored in is different under each model. That means the differences in the above GDP paths could be the result of reduced greenhouse gas emissions, or they could be due to other socio-economic differences between the RCPs’ design. But they at least suggest that a future of extremely aggressive carbon-cutting can be compatible with a future of strong global economic growth.

There’s a reason for this. Climate change means more droughts and altered rain patterns, leading to greater food insecurity. It means constricted freshwater supplies and heat waves, putting more strain on the infrastructure of cities and communities. It means less water to help run power stations and manufacturing processes, and altered river flows that can render shipping lanes useless. It means stronger storms and extreme weather that cause more damage, and it even means new and larger climate areas diseases can travel in.

Add it all up, and it means a lot of possible damage to the economy. The RCP2.6 is the course of action most likely to keep us under two degrees Celsius of warming — the threshold above which climate change becomes really dangerous according to most scientists. But the RCP8.5 is the scenario most likely to get us near five degrees Celsius of warming, an outcome summed up by David Roberts of Grist as “hell on earth.”

Worse, the IPCC reports are consensus documents between many players. That leads them to be conservative in their climate projections, with a tendency to lowball their estimates of the worst case scenarios. So the consequences for the climate — and thus for the economy — could in fact be much worse than the RCP8.5 modeling accounts for.

HT: Skeptical Science


The original version of this piece argued that the GDP paths for the different RCPs demonstrated that cutting carbon emissions would lead to stronger economic growth. That’s incorrect, for the reasons outlined above, and the post has been updated accordingly. We regret the error.

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