What Does “Climate Change” Mean? Does A Lack Of Preciseness In Its Definition Discourage Effective Discussion Of The Risks From Climate On Key Societal And Environmental Resources?

The term “climate change” is used by the media, funding agencies and in professional journals (e.g. see and see) but without a clear and adequate definition as to what this term means.  Here are a few definitions

1. Dictionary.com – climate change – a long-term change in the earth’s climate, especially a change due to an increase in the average atmospheric temperature: Melting glaciers imply that life in the Arctic is affected by climate change.

2.  The EPA -

Climate change is a problem that is affecting people and the environment. Greater energy efficiency and new technologies hold promise for reducing greenhouse gases and solving this global challenge. EPA’s website provides information on climate change for communities, individuals, businesses, states, localities and governments.

and from EPA FAQ

How are the terms climate change, global warming, and global change different?

The  term climate change is often used as if it means the same thing as the term  global warming. According to the National Academy of Sciences, however, “the  phrase ‘climate change’ is growing in preferred use to ‘global warming’ because  it helps convey that there are [other] changes in addition to rising  temperatures.” Climate change refers to any distinct change in measures of  climate lasting for a long period of time. In other words, “climate change”  means major changes in temperature, rainfall, snow, or wind patterns lasting  for decades or longer. Climate change may result from:

  • natural factors, such  as changes in the Sun’s energy or slow changes in the Earth’s orbit around the  Sun;
  • natural processes  within the climate system (e.g., changes in ocean circulation);
  • human activities that  change the atmosphere’s makeup (e.g, burning fossil fuels) and the land surface  (e.g., cutting down forests, planting trees, building developments in cities  and suburbs, etc.).

Global  warming is an average increase in temperatures near the Earth’s surface and in  the lowest layer of the atmosphere. Increases in temperatures in our Earth’s  atmosphere can contribute to changes in global climate patterns. Global warming  is probably the most talked about climate change we are experiencing, but is  just one of many changes along with precipitation levels, storm intensity, etc.  Global warming can be considered part of climate change along with changes in  precipitation, sea level, etc.

Global  change is a broad term that refers to changes in the global environment,  including climate change, ozone depletion, and land-use change.

3.  IPCC – Climate change

Climate change refers to a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer). Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.
Note that the Framework Convention on Climate Change (UNFCCC), in its Article 1, defines “climate change” as:  “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”. The UNFCCC thus makes a distinction between “climate change” attributable to human activities altering the atmospheric composition, and “climate variability” attributable to natural causes.

These diverse definitions need to be more focused, if we are going to build an agreement among scientists, policymakers and the public as to what is meant when the term “climate change” is used.    In Chapter 6 in the book

Climate Fix - What Scientists and Politicians Won’t Tell You About Global Warming 2010 by Roger A. Pielke Jr. Basic Books

there is a very insightful discussion of the subject as to what is meant by the term “climate change” and the resulting confusion and misunderstandings when more than one definition is used.  As written on page 145 of Climate Fix, in relation to the United Nations Framework Convention on Climate Change” definition,

“The IPCC adopts a broader definition of “climate change” that is more scientifically accurate. Claims that climate policy should be based on the work of the IPCC typically fail to recognize that the policy community has rejected the most fundamental statement of the IPCC on the issue – the very definition of “climate change”.

On Judy Curry’s weblog Climate Etc, she has reported on an article by Richard Betts in her post 2 perspectives on communicating climate science where Richard writes

But climate science is not a single-issue subject.  It is not carried out solely to see whether cuts in greenhouse gas emissions are needed or not.  A further and increasingly important issue is to understand the changes and variability we are seeing in order to help us live with the ever-changing weather and climate…..discussions need to move on from being anchored in the usual one-dimensional policy debate.

Both Judy and I agree 100% with Richard’s post.

I would like to add to this discussion here.  First, as I presented in my post

Recommended Definitions of “Global Warming” And “Climate Change”

Climate Change is any multi-decadal or longer alteration in one or more physical, chemical and/or biological components of the climate system…..Thus climate change includes, for example, changes in fauna and flora, snow cover, etc which persists for decades and longer. Climate variability can then be defined as changes which occur on shorter time periods.

In addition, when assessing the vulnerability of key resources (such as water resources, food, energy, human health and ecosystem function) with respect to climate (as well as the threat from all environmental and social risks) the questions we need to ask are, as presented in our article

Pielke Sr., R.A., R. Wilby, D. Niyogi, F. Hossain, K. Dairuku, J. Adegoke, G. Kallos, T. Seastedt, and K. Suding, 2012: Dealing  with complexity and extreme events using a bottom-up, resource-based  vulnerability perspective. AGU Monograph on Complexity and  Extreme Events in Geosciences, in press.

1. Why is this resource important? How is it used? To what stakeholders is it valuable?

2. What are the key environmental and social variables that influence this resource?

3. What is the sensitivity of this resource to changes in each of these key variables? (This may include but is not limited to, the sensitivity of the resource to climate variations and change on short (days); medium (seasons) and long (multi-decadal) time scales).

4. What changes (thresholds) in these key variables would have to occur to result in a negative (or positive) outcome for this resource?

5. What are the best estimates of the probabilities for these changes to occur? What tools are available to quantify the effect of these changes? Can these estimates be skillfully predicted?

6. What actions (adaptation/mitigation) can be undertaken in order to minimize or eliminate the negative consequences of these changes (or to optimize a positive response)?

7. What are specific recommendations for policymakers and other stakeholders?

In this context, climate change is just one of a multitude of threats. Building a consensus among the diverse policy and political viewpoints based on the above 7 questions will be easier that continuing to force a one-dimensional view of climate change (either as narrowly defined by the UNFCCC) or more broadly by the IPCC) onto the policy and political communities.

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