This interview was originally published by Rutgers University’s Institute of Earth, Ocean, and Atmospheric Sciences. It has been condensed here. Read the full interview at this link. 

On October 6, 2018 the Intergovernmental Panel on Climate Change (IPCC) approved a special report titled “Global Warming of 1.5°C, an IPCC special report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change.”

In its press release the IPCC stated, “Limiting global warming to 1.5°C would require rapid, far-reaching and unprecedented changes in all aspects of society . . . With clear benefits to people and natural ecosystems, limiting global warming to 1.5°C compared to 2°C could go hand in hand with ensuring a more sustainable and equitable society.”

In this Q&A, the Director of the Rutgers Institute of Earth, Ocean, and Atmospheric Sciences (EOAS) and a professor in the Department of Earth and Planetary Sciences, Robert Kopp, responds to the report’s conclusions, and explains the difference between focusing on temperature targets versus net-zero emissions as goals to reduce global warming.

Kopp notes that the report’s focus on the speed with which net global carbon dioxide emissions must reach zero in order to stabilize climate at different levels of warming could advance a pivot away from a focus on temperature targets and toward a focus on eliminating net emissions.

“The traditional focus in climate policy discourse on temperature targets feeds a kind of fatalism that can be counterproductive,” he argues. “It’s a false but not uncommon idea that if we undershoot a temperature target, we will be safe, and if we overshoot, it will be catastrophic . . . Rather than focus on temperature targets, climate change mitigation policy should be oriented around one of the most critical challenges of this century: Getting net global greenhouse gas emissions to zero.”

Kopp, who is a lead author of an IPCC report being released in 2021, also describes the many scientific contributions EOAS scientists are making to this and other IPCC reports, how New Jersey will be impacted by rising temperatures, and steps individuals can take to reduce greenhouse gas emissions.

What are the most important actions the U.S. and other governments need to take immediately and long term in order to meet the IPCC’s recommendation that global warming not exceed a 1.5°C increase?

First off, let me clarify something regarding the role of the IPCC: it does not make recommendations. The goal of the IPCC is to provide policy-relevant scientific assessments, not to make policy recommendations. The new report was written in response to a request by the nations of the world that the IPCC assess the benefits and challenges of keeping warming below 1.5°C. It’s not the role of the IPCC to say that we should, or should not, do this.

Keeping warming below 1.5°C would require a radical and immediate transformation of global energy and agricultural systems in order to bring global net carbon dioxide emissions close to zero by 2050. It also requires either that CO₂ emissions are cut by about half from current levels over the next 12 years, or that we develop and massively deploy technologies for accelerating the natural removal of CO₂ after 2050.

These are both stretch goals to say the least.

That said, I want to emphasize a couple of crucial points:

First, climate change is not a binary thing. It’s just not the case that 1.4°C of warming is fine but 1.6°C is catastrophic. Every incremental increase in emissions leads to an incremental increase in temperature and thus to an incremental increase in the risks that society and ecosystems face. Every bit we do to reduce warming reduces the risk that we have to face.

Second, while lower levels of warming require faster decarbonization, stabilizing the climate at any level of warming – whether 1.5°C, 2.0°C, 2.5°C, or higher – requires achieving zero net CO₂ emissions. Every ton of CO₂ put into the air creates a small increment of warming that will last for millennia; only stopping net emissions can stop warming.

I personally hope that the emphasis this report places on the need for net-zero emissions – a need also noted in the Paris Climate Agreement – will drive a shift in climate policy discourse away from temperature targets and toward a focus on how quickly we can get to net zero.

I think that the traditional focus in climate policy discourse on temperature targets feeds a kind of fatalism that can be counterproductive. It’s a false but not uncommon idea that if we undershoot a temperature target, we will be safe, and if we overshoot, it will be catastrophic.  Indeed, we saw this false idea in some of the press coverage of the 1.5°C report.

Moreover, whereas the temperature response to greenhouse gas emissions is driven by a variety of feedbacks, some poorly known, humans have direct control over the level of these emissions. Whereas a goal of stabilizing temperature at a specific level cannot be translated directly into policy, the goal of net-zero emissions can be.

I would argue that, rather than focus on temperature targets, climate change mitigation policy should be oriented around one of the most critical challenges of this century: Getting net global greenhouse gas emissions to zero.

How might New Jersey change, in terms of sea-level rise, changes to weather and local ecosystems, and other impacts if the target of 1.5°C is not met?

Kopp: Of all the risks New Jersey faces as a result of climate change, the impacts of sea-level rise and coastal storms are – among those that economists, including my colleagues in the Climate Impact Lab, are currently able to quantify – the greatest. And here the difference between 1.5°C and 2.0°C is small, at least at first. Work we’ve done with collaborators at Princeton Universityand Climate Central suggests that the difference between 1.5°C and 2.0°C is a bit over half a foot of sea-level rise between now and 2150. For warming beyond 2.0°C, though, the differences may be much larger – ten feet of sea-level rise in New Jersey by 2100 is not out of the question in a world of unbridled emissions growth, whereas in a 2°C world, sea-level rise in excess of five feet over the same time scale is extremely unlikely.

Are there actions individuals can take to help reduce global warming?

Individuals can assess their carbon footprints using a variety of tools and take actions to reduce these footprints – whether that’s reducing their use of fossil-fueled vehicles, increasing the efficiency of their home air conditioning and heating systems, or reducing meat consumption.

But climate change is ultimately a societal challenge, and it requires policy to address: thus, the most important actions individuals can take are to talk about climate change, to vote, and to ensure that their elected officials hear their concerns and implement effective policy to achieve decarbonization and manage unavoided risks.