Thinking beyond temperature when setting carbon emissions goals

Kristian Vinkenes

At the 1996 international climate talks in Kyoto, a specific goal for minimizing the harmful effects of climate change was selected—keep warming within 2°C of preindustrial levels. Given that the globe has already warmed almost 1°C, meeting that goal was clearly going to take some serious work. The lack of real progress in reducing greenhouse emissions since then doesn’t exactly inspire optimism about meeting that goal.

But does the 2°C goal truly represent a minimal impact? A study published this week in Nature shows that policy makers would do well to consider specific goals for more than just global average surface temperature. If they do, they might find that even greater emissions reductions are warranted.

The study examined five targets beyond global temperature: sea level rise caused by thermal expansion (not melting ice), ocean acidification in the sensitive Southern Ocean, a measure of acidification elsewhere that would harm coral reefs, reduction of cropland productivity, and carbon lost from cropland soils. The numbers that were used for each of these targets are actually unimportant. The point was to discover whether having multiple targets could change the emissions reductions necessary to hit them.