Note: Dr. Judith Curry is President (co-owner) of Climate Forecast Applications Network (CFAN) and was previously Professor and Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology.
Dr. Curry writes:
We have been hearing increasingly shrill rhetoric from Extinction Rebellion and other activists about the ‘existential threat’ of the ‘climate crisis’, ‘runaway climate chaos’, etc. In a recent op-ed, Greta Thunberg stated: “Around 2030 we will be in a position to set off an irreversible chain reaction beyond human control that will lead to the end of our civilization as we know it.” From the Extinction Rebellion: “It is understood that we are facing an unprecedented global emergency. We are in a life or death situation of our own making.”
It is more difficult tune out similar statements from responsible individuals representing the United Nations. In his opening remarks for the UN Climate Change Conference this week in Madrid (COP25), UN Secretary General Antonio Guterres said that “the point of no-return is no longer over the horizon.” Hoesung Lee, the Chair for the Intergovernmental Panel on Climate Change (IPCC), said “if we stay on our current path, [we] threaten our existence on this planet.”
So . . . exactly what should we be worried about? Consider the following statistics:
Over the past century, there has been a 99% decline in the death toll from natural disasters, during the same period that the global population quadrupled.
While global economic losses from weather and climate disasters have been increasing, this is caused by increasing population and property in vulnerable locations. Global weather losses as a percent of global GDP have declined about 30% since 1990.
While the IPCC has estimated that sea level could rise by 0.6 meters by 2100, recall that the Netherlands adapted to living below sea level 400 years ago.
Crop yields continue to increase globally, surpassing what is needed to feed the world. Agricultural technology matters more than climate.
The proportion of world population living in extreme poverty declined from 36% in 1990 to 10% in 2015.
While many people may be unaware of this good news, they do react to each weather or climate disaster in the news. Activist scientists and the media quickly seize upon each extreme weather event as having the fingerprints of manmade climate change — ignoring the analyses of more sober scientists showing periods of even more extreme weather in the first half of the 20th century, when fossil fuel emissions were much smaller.
So . . . why are we so worried about climate change? The concern over climate change is not so much about the warming that has occurred over the past century. Rather, the concern is about what might happen in the 21st century as a result of increasing fossil fuel emissions. Emphasis on ‘might.’
Alarming press releases are issued about each new climate model projection that predicts future catastrophes from famine, mass migrations, catastrophic fires, etc. However these alarming scenarios of the 21st century climate change require that, like the White Queen in Alice and Wonderland, we believe ‘six impossible things before breakfast’.
The most alarming scenarios of 21st century climate change are associated with the RCP8.5 greenhouse gas concentration scenario. Often erroneously described as a ‘business as usual’ scenario, RCP8.5 assumes unrealistic trends long-term trends for population and a slowing of technological innovation. Even more unlikely is the assumption that the world will largely be powered by coal.
In spite of the implausibility of this scenario, RCP8.5 is the favored scenario for publications based on climate model simulations. In short, RCP8.5 is a very useful recipe for cooking up scenarios alarming impacts from manmade climate change. Which are of course highlighted and then exaggerated by press releases and media reports.
Apart from the issue of how much greenhouse gases might increase, there is a great deal of uncertainty about much the planet will warm in response to a doubling of atmospheric carbon dioxide – referred to as ‘equilibrium climate sensitivity’ (ECS). The IPCC 5th Assessment Report (2013) provided a range between 1 and 6°C, with a ‘likely’ range between 1.5 and 4.5ºC.
In the years since the 5th Assessment Report, the uncertainty has grown. The latest climate model results – prepared for the forthcoming IPCC 6th Assessment Report – shows that a majority of the climate models are producing values of ECS exceeding 5°C. The addition of poorly understood additional processes into the models has increased confusion and uncertainty. At the same time, refined efforts to determine values of the equilibrium climate sensitivity from the historical data record obtain values of ECS about 1.6°C, with a range from 1.05 to 2.7°C.
With this massive range of uncertainty in the values of equilibrium climate sensitivity, the lowest value among the climate models is 2.3°C, with few models having values below 3°C. Hence the lower end of the range of ECS is not covered by the climate models, resulting in temperature projections for the 21st century that are biased high, with a smaller range relative to the range of uncertainty in ECS.
With regards to sea level rise, recent U.S. national assessment reports have included a worst-case sea level rise scenario for the 21st century of 2.5 m. Extreme estimates of sea level rise rely on RCP8.5 and climate model simulations that are on average running too hot relative to the uncertainty range of ECS. The most extreme scenarios of 21st century sea level rise are based on speculative and poorly understood physical processes that are hypothesized to accelerate the collapse of the West Antarctic Ice Sheet. However, recent research indicates that these processes are very unlikely to influence sea level rise in the 21st century. To date, in most of the locations that are most vulnerable to sea level rise, local sinking from geological processes and land use has dominated over sea level rise from global warming.
To further complicate climate model projections for the 21st century, the climate models focus only on man-made climate change – they make no attempt to predict natural climate variations from the sun’s output, volcanic eruptions and long-term variations in ocean circulation patterns. We have no idea how natural climate variability will play out in the 21st century, and whether or not natural variability will dominate over man-made warming.
We still don’t have a realistic assessment of how a warmer climate will impact us and whether it is ‘dangerous.’ We don’t have a good understanding of how warming will influence future extreme weather events. Land use and exploitation by humans is a far bigger issue than climate change for species extinction and ecosystem health.
We have been told that the science of climate change is ‘settled’. However, in climate science there has been a tension between the drive towards a scientific ‘consensus’ to support policy making, versus exploratory research that pushes forward the knowledge frontier. Climate science is characterized by a rapidly evolving knowledge base and disagreement among experts. Predictions of 21st century climate change are characterized by deep uncertainty.
As noted in a recent paper co-authored by Dr. Tim Palmer of Oxford University, https://www.pnas.org/content/pnas/early/2019/11/26/1906691116.full.pdf, there is “deep dissatisfaction with the ability of our models to inform society about the pace of warming, how this warming plays out regionally, and what it implies for the likelihood of surprises.” “Unfortunately, [climate scientists] circling the wagons leads to false impressions about the source of our confidence and about our ability to meet the scientific challenges posed by a world that we know is warming globally.”
We have not only oversimplified the problem of climate change, but we have also oversimplified its ‘solution’. Even if you accept the climate model projections and that warming is dangerous, there is disagreement among experts regarding whether a rapid acceleration away from fossil fuels is the appropriate policy response. In any event, rapidly reducing emissions from fossil fuels to ameliorate the adverse impacts of extreme weather events in the near term increasingly looks like magical thinking.
Climate change – both man-made and natural – is a chronic problem that will require continued management over the coming centuries.
We have been told that climate change is an ‘existential crisis.’ However, based upon our current assessment of the science, the climate threat is not an existential one, even in its most alarming hypothetical incarnations. However, the perception of man-made climate change as a near-term apocalypse and has narrowed the policy options that we’re willing to consider. The perceived ‘urgency’ of drastically reducing fossil fuel emissions is forcing us to make near term decisions that may be suboptimal for the longer term. Further, the monomaniacal focus on elimination of fossil fuel emissions distracts our attention from the primary causes of many of our problems that we might have more success in addressing in the near term.
Common sense strategies to reduce vulnerability to extreme weather events, improve environmental quality, develop better energy technologies and increase access to grid electricity, improve agricultural and land use practices, and better manage water resources can pave the way for a more prosperous and secure future. Each of these solutions is ‘no regrets’ – supporting climate change mitigation while improving human well being. These strategies avoid the political gridlock surrounding the current policies and avoid costly policies that will have minimal near-term impacts on the climate. And finally, these strategies don’t require agreement about the risks of uncontrolled greenhouse gas emissions.
We don’t know how the climate of the 21st century will evolve, and we will undoubtedly be surprised. Given this uncertainty, precise emissions targets and deadlines are scientifically meaningless. We can avoid much of the political gridlock by implementing common sense, no-regrets strategies that improve energy technologies, lift people out of poverty and make them more resilient to extreme weather events.
The extreme rhetoric of the Extinction Rebellion and other activists is making political agreement on climate change policies more difficult. Exaggerating the dangers beyond credibility makes it difficult to take climate change seriously. On the other hand, the extremely alarmist rhetoric has frightened the bejesus out of children and young adults.
JC message to children and young adults: Don’t believe the hype that you are hearing from Extinction Rebellion and the like. Rather than going on strike or just worrying, take the time to learn something about the science of climate change. The IPCC reports are a good place to start; for a critical perspective on the IPCC, Climate Etc. is a good resource.
Climate change — man-made and/or natural — along with extreme weather events, provide reasons for concern. However, the rhetoric and politics of climate change have become absolutely toxic and nonsensical.
In the mean time, live your best life. Trying where you can to lessen your impact on the planet is a worthwhile thing to do. Societal prosperity is the best insurance policy that we have for reducing our vulnerability to the vagaries of weather and climate.
JC message to Extinction Rebellion and other doomsters: Not only do you know nothing about climate change, you also appear to know nothing of history. You are your own worst enemy — you are triggering a global backlash against doing anything sensible about protecting our environment or reducing our vulnerability to extreme weather. You are making young people miserable, who haven’t yet experienced enough of life to place this nonsense in context.