Pielke's Weekly Memo #2: What is climate change?

Remarkably, the UN organizations that oversee climate science and climate policy each use a different definition of "climate change." Here is why that matters.

Note: Ungated 31 October 2022 -RP

Believe it or not, the United Nations Framework Convention on Climate Change (FCCC), focused on international policy, and the Intergovernmental Panel on Climate Change (IPCC), focused on scientific assessments in support of the FCCC, use different definitions of climate change. The two definitions are not compatible. This lack of coherence has contributed to a number of pathologies in international climate policy, including the institutionalization of a bias against adaptation, which I’ll discuss today.

Under the FCCC definition, “adaptation” refers only to new actions in response to climate changes that are attributed to greenhouse gas emissions. It does not refer to improving adaptation to climate variability or change that are not attributed to greenhouse gas emissions. From the perspective of the FCCC definition, without the increasing greenhouse gases, climate would not change, and the new adaptive measures would therefore be unnecessary. It follows that these new adaptations represent costs that would be unnecessary if climate change could be prevented by mitigation strategies. Under the logic of the FCCC definition of climate change, adaptation represents a cost of climate change, and other benefits of these adaptive measures are not counted.

The bias against adaptation has percolated into research and assessment. It is reflected in the confused attitude that the IPCC has taken toward the definition of climate change across its three working groups. Its working group on science prefers (and indeed developed) the broad IPCC definition. The working group on mitigation prefers the FCCC definition; and the working group on impacts, adaptation, and vulnerability variously uses both definitions.

One result of this confusion is an implicit bias against adaptation policies in the IPCC reports, and by extension, in policy discussions. For instance, the discussion of “Loss and Damage” under the FCCC has often been hamstrung by this issue, as questions such as the following are often raised in debates.

• What damages related to climate can be attributed to greenhouse gases?

• What about the societal conditions that create exposures and vulnerabilities regardless the precise causality behind weather events?

• Who is responsible for overall damage in the context of complex causality?

• Is attribution to greenhouse gases necessary to free up and justify international funding? And on and on it goes.

The bias against adaptation occurs despite the fact that adaptation policies make sense regardless of attribution specifics. That’s because the world is already committed to some degree of climate change and many communities are ill prepared for any change. Many, if not most, adaptive measures would make sense even if there were no greenhouse gas-related climate change. Under the logic of the FCCC definition of climate change, there is exceedingly little room for efforts to reduce societal or ecological vulnerability to climate variability and changes that are the result of factors other than greenhouse gases. From the broader IPCC perspective on climate change, adaptation policies also have benefits to the extent that they lead to greater resilience of communities and ecosystems to climate change, variability, and particular weather phenomena.

We can readily see both the confusion and the conflicts that result. For instance, in discussion of climate policy it is common to see those looking at adaptation and mitigation as opposing strategies rather than as complements. Under such a view adaptation is recommend only to the extent that proposed mitigation strategies will be unable to prevent changes in climate. Adaptation is thus a cost of failed mitigation, and a bad thing. From the perspective of adaptation, the FCCC approach serves as a set of blinders, directing attention away from adaptation measures that make sense under any scenario of future climate. In the face of the obvious limitations of mitigation-only policies, reconciling the different definitions of climate change becomes more important as nations around the world necessarily move toward a greater emphasis on adaptation.

We saw this dynamic play out in the recent IPCC Working Group 2 report, which centered its focus on mitigation over adaptation. As I recently wrote:

A new focus on mitigation is explicit, with the IPCC WG2 noting (1-31) that its focus “expands significantly from previous reports” and now includes “the benefits of climate change mitigation and emissions reductions.” This new emphasis on mitigation colors the entire report, which in places reads as if adaptation is secondary to mitigation or even impossible. The IPCC oddly presents non-sequiturs tethering adaptation to mitigation, “Successful adaptation requires urgent, more ambitious and accelerated action and, at the same time, rapid and deep cuts in greenhouse gas emissions.”

The FCCC definition of climate change shapes not only the politics of climate change but also how research agendas are prioritized and funded. One result has been the growing focus on single-event attribution. Such research, admittedly designed for media impact, is irrelevant to adaptation decision making – What adaptive decision turns on the question of what would today’s weather be if humans never invented fire and then burned fossil fuels? To the extent that research becomes detached from the near-term need of decisionmakers, we miss opportunities to help them to improve reduce vulnerabilities to climate.

The broader IPCC definition of climate change sets the stage for consideration of a wide array of mitigation and adaptation policies. Under the broader definition, the IPCC assessments show clearly that the effects of climate change on people and ecosystems are not the result of a linear process in which a change in climate disrupts an otherwise stable society or environment. The real world is much more complex for several reasons.

First, society and the environment undergo constant and dramatic change as a result of human activities. People build on exposed coastlines, in floodplains, and in deserts. Development, demographics, wealth, policies, and political leadership change over time, sometimes significantly and unexpectedly. These factors and many more contribute to the vulnerability of populations and ecosystems to the impacts of climate-related phenomena. Different levels of vulnerability help to explain, for example, why a tropical cyclone that makes landfall in the United States has profoundly different effects than an identical storm that makes landfall in Haiti. There are many reasons why a particular community or ecosystem may experience adverse climate effects under conditions of climate stability. For example, a flood in an unoccupied floodplain may be noteworthy, but a similar flood in a heavily populated floodplain is a disaster. In this example, the development of the floodplain is the “interference” that makes the flood dangerous. Under the FCCC definition of climate change, any such societal change would not be cause for action, even though serious and adverse effects on people and ecosystems may result.

Second, climate changes on all time scales and for many reasons, not all of which are fully understood or quantified. Policy should be robust to an uncertain climate future, regardless of the cause of particular climate changes. Consider abrupt climate change. A 2003 review paper (of which I was a coauthor) in Science on abrupt climate change observes that

“Such abrupt changes could have natural causes, or could be triggered by humans and be among the ‘dangerous anthropogenic interferences’ referred to in the [FCCC]. Thus, abrupt climate change is relevant to, but broader than, the FCCC and consequently requires a broader scientific and policy foundation.”

The IPCC definition provides such a foundation.

An approach to climate change more consistent with the realities of science and the needs of decisionmakers would begin with a shared definition of climate among the science and policy communities that can accommodate complexity and uncertainty.

Read more for free (no paywall!) here: Pielke Jr, R. A. (2005). Misdefining “climate change”: consequences for science and action. Environmental Science & Policy, 8(6), 548-561.