6 questions we need to answer after the Paris climate deal

Reuters/Stephane Mahe

Much has been written about the challenge of achieving the targets set out in the Paris climate agreement, which calls for global warming to be held well below 2℃ and ideally within 1.5℃ of pre-industrial temperatures.

That’s the headline goal, but the Paris agreement also calls for a strong focus on climate science as well as on curbing greenhouse emissions.

Article 7.7c of the agreement specifically calls for:

Strengthening scientific knowledge on climate, including research, systematic observation of the climate system and early warning systems, in a manner that informs climate services and supports decision-making.

The next paragraph also calls on countries to help poorer nations, which have less scientific capability, to do the same.

But what are the many elements of climate science that need strengthening to achieve the aims of the Paris agreement? Here are six questions that need answers.

What do the targets mean?

What do the 2℃ and 1.5℃ targets imply for our climate and adaptation responses? Even warming of 2℃ will have significant impacts for humans and natural systems, albeit much less than would occur if we allowed warming to continue unchecked.

Still, climate science needs to clarify what is gained by meeting the 1.5℃ and 2℃ targets, and the consequences of missing them.

Are we on track?

It will be essential to monitor the climate system over the coming years and decades to see whether our efforts at curbing warming are delivering the expected benefits, or if more measures are needed.

The path to these ambitious temperature targets will not be smooth – there will be periods of rapid warming interspersed with periods of slower warming. We will not meet the targets if the world relaxes on mitigation efforts because of a short-term slowing in the rate of warming as a result of natural variability, such as we saw between 1998 and 2013.

Greenhouse gas concentrations, global temperatures, rainfall and water balance changes, extreme weather events, ocean heat content, sea level and terrestrial and marine carbon sinks are all vitally important elements to track. A focus on surface temperature alone is not sufficient.

What are the tipping points in the climate system?

Tipping points are thresholds beyond which there will be large, rapid and possibly irreversible changes in the climate system.

The Greenland and Antarctic ice sheets are one example – beyond a certain level, warming will cause large and irreversible loss of ice, and sea level rise of many meters over the ensuing centuries. Thresholds also exist for ecosystems, such as the Great Barrier Reef, and the services they provide, including food production and water supply.

We need to know what these thresholds are, the consequences of crossing them, and how much and how fast we will have to reduce emissions in order to avoid this.