A lower limit for future climate emissions

February 24, 2016, International Institute for Applied Systems Analysis
A composite image of the Western hemisphere of the Earth. Credit: NASA

In a comprehensive new study published in the journal Nature Climate Change, researchers propose a limit to future greenhouse gas emissions—or carbon budget—of 590-1240 billion tons of carbon dioxide from 2015 onwards, as the most appropriate estimate for keeping warming to below 2°C, a temperature target which aims to avoid the most dangerous impacts of climate change.

The study finds that the available budget is on the low end of the spectrum compared to previous estimates—which ranged from 590 to 2390 billion tons of carbon dioxide for the same time period—lending further urgency to the need to address .

"In order to have a reasonable chance of keeping global warming below 2°C, we can only emit a certain amount of carbon dioxide, ever. That's our ," says IIASA researcher Joeri Rogelj, who led the study. "This has been known for about a decade and the physics behind this concept are well-understood, but many different factors can lead to carbon budgets that are either slightly smaller or slightly larger. We wanted to understand these differences, and provide clarity on the issue for policymakers and the public."

"This study shows that in some cases we have been overestimating the available budget by 50 to more than 200%. At the high end, this is a difference of more than 1000 billion tons of carbon dioxide," says Rogelj.

Estimates for a carbon budget consistent with the 2°C target have varied widely. The new study provides a comprehensive analysis of these differences. The researchers identified that the variation in carbon budgets stemmed from differences in scenarios and methods, and the inclusion of other human activities that can affect the climate, for example the release of other greenhouse gases like methane. Previous research suggested that the varying contribution of other human activities would be the main reason for carbon budget variations, but surprisingly, the study now finds that methodological differences contribute at least as much.

The proposed budget accounts for warming of all human activities and greenhouse gases and is based on detailed scenarios that simulate low-carbon futures.

Rogelj says, "We now better understand the carbon budget for keeping below 2 degrees. This carbon budget is very important to know because it defines how much we are allowed to release into the atmosphere, ever. We have figured out that this budget is at the low end of what studies indicated before, and if we don't start reducing our emissions immediately, we will blow it in a few decades."

Explore further: Climate 'carbon budget' soon maxed out: study

More information: Joeri Rogelj et al. Differences between carbon budget estimates unravelled, Nature Climate Change (2016). DOI: 10.1038/NCLIMATE2868

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2.1 / 5 (7) Feb 24, 2016
Time for electric cars, folks!

You will love them: Full torque at standstill, no noise, no oil and oil leaks, no filters, no tune-ups, no service except for windshield washer fluid. Mine has four stages of regeneration, meaning taking my foot off the gas slows down the car by generating electricity back into the battery. In downhill trips, we can put miles into the battery.

Having it for a few months means we have saved eleven fill-ups of about 15 gallons each, and those eleven trips to a gas station. We "fill up" at home now when the power is cheap, on an EV-1 (or is it the EV-A?), schedule.

With better range, we will all have them.
4.2 / 5 (5) Feb 24, 2016
absolutely, I love my electric car! I have paid for half the cost of the car in fuel savings
(it was second hand and fuel is expensive in the UK due to heavy taxes).
4 / 5 (4) Feb 24, 2016
I am looking forward to owning one. I'm fairly sure the next car I buy will be electric. Range is a significant part of it - right now I believe only a Tesla would work for me. I'm looking forward to the new model later this year. Could be the right one....
2.3 / 5 (3) Feb 24, 2016
Zzzz, I think in a year, it will be what you need. the new ones already have better batteries than the one I drive now. I expect to replace these eventually, and use them for home storage, getting ones with better performance for the car. But with none of the reciprocating and complex movement, friction and gases of the ICE, it is as simple, quiet, and reliable as driving your toaster.

We had to wait until we could access some savings to do it.
5 / 5 (2) Feb 29, 2016
As an Australian, I've had to hold off on the purchase of an electric car. The distances are simply too great and so recharging stations haven't exactly proliferated. But I've reduced my driving significantly and am looking forward to finally going electric

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