Dr. X answers your questions about the climate
Don't learn about climate science from the media. They're just messing with your minds.
From Claire—Dr. X is an old friend and a distinguished climate scientist. Read his first post and the explanation for his pseudonym here.
By Dr. X
For my second post, I had planned to share some general thoughts on why people accept, or do not accept, the scientific consensus on climate change. First, Claire pointed me to a series of questions from Eric Dyke, and I began writing some replies. Then she pointed me to a second post in which Mr. Dyke confessed he was “joining the Patersons,” a little less skeptical, and wants to learn more. I found this so encouraging that I’ve focused this post entirely on his questions. Because he wrote that he looked forward to this, I trust he won’t mind. I do this not at all to single him out as misinformed, but because his questions are shared by much of the public.
From the start, let me say that I make no assumptions about Mr. Dyke’s political views, nor have they anything to do with this discussion. I will try to make clear when I’m speaking as a scientist, as opposed to a citizen. As a climate scientist, I generally know what I’m talking about. I’m not infallible: If you think I’ve gotten the science wrong, correct me.
I won’t drown you in citations, but if any point is unclear, I can point you to more detailed studies. Some are behind firewalls, but I can make copies available on request to Claire. On non-scientific matters, I will try not to overstep my bounds.
Let me address Mr. Dyke’s questions in turn.
Mr. Dyke: For the last ten years I have been reading all I can about climate change. I am going to state a series of observations and look forward to them being either corrected or validated.1
[The observations are listed below.]
Dr. X: Some of these statements are found often in the media, but they are not scientifically supported. The right-wing and the left-wing media are both prone to repeating things no serious scientist would stay. If you’re curious about climate science, I advise staying away from the media, entirely. Especially, read no article that is clearly meant to target your emotions. The business model for journalism favors working readers into a lather above fact-checking. If you want to know what climate scientists really think—rather than what they’re said to think—I suggest reading peer-reviewed science literature. Here’s a rule of thumb: If reading doesn’t bore you or confuse you at first, it’s probably not good science. But once you start to figure things out and see the big picture, it’s thrilling.
Scientists get things wrong, too. But the business model for science doesn’t favor getting things wrong; whereas in a hyperpolarized democracy, the business model for journalism inevitably will. The business model for science is different. To stay employed, scientists need to publish peer-reviewed papers; to succeed at peer review, they need thorough, careful arguments, drawing careful lines between what’s well-founded and what’s more speculative. Many papers end with a disclaimer to the effect that “more work is needed to understand this problem better.” This leads to more papers, and eventually what we can call well-established knowledge—and not much drama.
The reports of the Intergovernmental Panel on Climate Change are very well vetted—a single chapter could have dozens or even hundreds of reviewers—so much that they usually err on the side of caution. The authors are scrupulous in using probabilistic language (virtually certain, extremely likely, more likely than not, etc.), and they state whether the conclusions have high, medium, or low confidence. I suggest starting with the Summary for Policymakers, then reading the chapters that most interest you. The IPCC Fifth Assessment Report from 2014 is a bit dated, but the Sixth Assessment will appear in the coming year. Also, recent IPCC Special Reports treat, for example, the impact of global warming above 1.5 degrees C, or the oceans and cryosphere.
Mr. Dyke: There appears to be global warming taking place, at least in the Northern Hemisphere. Not so clear in the South.
Dr. X: Both hemispheres are warming, and the Northern Hemisphere is warming faster than the Southern Hemisphere. This is known as the Interhemispheric Temperature Asymmetry. This difference is expected, in part, because the Northern Hemisphere has more land than the Southern Hemisphere. Land masses warm faster than the ocean because they have a lower heat capacity. Also, the Arctic is expected to warm faster than the Antarctic. The Arctic warms as the sea ice cover thins and retreats. The ice is replaced by an ocean surface that absorbs more sunlight. The Antarctic continent, on the other hand, is so high and cold that there is little surface melting, thus no change in solar absorption.
The asymmetry is illustrated in this map:
The map projection is misleading, like most map projections, in that it exaggerates the area of the poles compared to the tropics. Keep in mind that half the Earth’s area lies between 30oN and 30oS. You can see extreme warming in the Arctic, strong warming in Northern mid-latitudes and the tropics, moderate warming in Southern mid-latitudes, and a complicated mix of warming and cooling in the Antarctic. This pattern is consistent with scientific understanding of climate change driven by greenhouse gases.
Mr. Dyke: The conventional wisdom is that GHGs are causing it, primarily CO2, methane, nitrous oxide, and water vapor. But other causes are possible. The Sun’s activity or a change in ocean currents could also explain it. (Dr. Ian Clarke, a researcher of Paleoclimatology at University of Ottawa, states there is a very good correlation between the Sun’s solar energy and global temperatures. He also states that as temperatures increase, the oceans degas CO2, causing increased levels in the atmosphere. So, temperature may drive CO2, not the reverse. CO2 is not a thermostat that controls temperatures. And increased levels of CO2 from human activities may well have beneficial effects.)
Dr. X: Indeed, the scientific consensus is that warming since the mid 20th century has been driven mainly by GHGs. Other causes, including changes in solar and volcanic activity, are possible in principle, but have been ruled out by observation. For example, we can measure the solar energy reaching the Earth, and it is not correlated with recent warming. Nor can changes in ocean currents explain the recent warming. Changes in ocean circulation account for many of the natural variations in climate, but generally they redistribute heat rather than warming the entire Earth.
Causality between temperature and CO2 is mutual, in part because the capacity of the ocean to store dissolved carbon varies inversely with temperature. It is true that as temperatures rise, the oceans hold less CO2, so some of the CO2 will degas to the atmosphere. But the increasing CO2 in the atmosphere (now 420 ppm, compared to about 280 ppm before 1850) has a fossil signal; that is, it is relatively depleted in the isotopes C-13 and C-14. Thus, most of it must have come from burning of fossil fuels, not from ocean outgassing.
As the ocean warms, it will have less capacity to absorb the CO2 that humans emit. Thus, a growing fraction of the emitted CO2 could stay in the atmosphere, unless land surfaces increase their carbon uptake.
Mr. Dyke: What is clear is that predicting the effects of all the factors on climate is extremely difficult and the climate models require assumptions and simplifications. So far, the models have not been verified by empirical observations of the climate.
Dr. X: Climate prediction is indeed difficult, and models require assumptions and simplifications. But climate models are very good at the essential physics: For example, computing how much incoming and outcoming radiation are absorbed, transmitted, or reflected by different gases in the atmosphere; modeling large-scale atmospheric and ocean currents (the Hadley cell, prevailing mid-latitude winds, ocean boundary currents, etc.); and conserving energy and water.
Climate models have been extensively validated by empirical observations. They are not perfect, but they are improving. They are good enough to make hindcasts of how the climate has responded to past GHG emissions, and credible forecasts of its response to future emissions, within stated uncertainty ranges.
Mr. Dyke: Activists claim, and the media repeats ad nauseum, that global warming is causing:
increased forest fires;
droughts and floods;
increased frequency and intensity of tropical storms;
rising oceans, to the extent that inhabited areas will be underwater;
polar bears, the poster child for global warming, to struggle to survive in an Arctic without sea ice cover;
myriad other ills which the media breathlessly reports, including racial inequities.
Dr. X: Activists will not provide the best available science information, and what’s reported in the media is of uneven credibility. Here’s how I would summarize the evidence for the effects mentioned:
There is strong evidence that climate change is contributing to a greater number and severity of forest fires, droughts, and floods. In most cases, it is not possible to attribute a particular weather event to climate change, but only to say that climate change makes such events more likely.
On physical grounds, we would expect global warming to enable stronger storms, because a warmer atmosphere holds more of the water vapor that supplies energy for storms. But I am not aware of evidence that the overall frequency of storms is increasing. This is often misreported.
It is virtually certain that rising temperatures are responsible for most global mean sea-level rise, in the form of thermal expansion of seawater and melting of glaciers and ice sheets. Sea-level rise is not uniform; it also depends on local and regional factors such as ground subsidence and post-glacial rebound. Whether and when a particular region becomes uninhabitable depends on many factors, including the residents’ capacity to adapt.
Arctic sea ice cover is decreasing, which makes life harder for animals that use sea ice as a hunting platform. Polar bears may be able to survive on nearby land or in regions that retain sea ice. I am personally fond of polar bears (at a safe distance), but I agree that climate reporting is often imbalanced in favor of charismatic species as opposed to others that are equally or more threatened.
Obviously, global warming is not responsible for historical racial inequities. Speaking as a citizen: To the extent that historical inequities have rendered some groups less able than others to adapt to the effects of climate change, these groups are likely to suffer disproportionately.
Mr. Dyke: The Canadian Forest Service reports that the incidence of forest fires is lower than they have ever been. They show a steady decline over the last 50 years. I suspect if records are consulted, the forest fires in California, Australia, and Brazil, and in less reported Namibia, are all within historical norms.
Dr. X: Forest fires have many causes, including climate-related warming and drying as well as poor forest management. And of course, fires occur naturally in healthy forests. But climate change does contribute to increasingly severe wildfires.
According to the California Department of Forestry and Fire Protection,
[w]hile wildfires are a natural part of California’s landscape, the fire season in California and across the West is starting earlier and ending later each year. Climate change is considered a key driver of this trend. Warmer spring and summer temperatures, reduced snowpack, and earlier spring snowmelt create longer and more intense dry seasons that increase moisture stress on vegetation and make forests more susceptible to severe wildfire. The length of fire season is estimated to have increased by 75 days across the Sierras and seems to correspond with an increase in the extent of forest fires across the state .”
Mr. Dyke: There has been no increase in either droughts or floods in Canada.
Dr. X: This is an example of what we call the backyard fallacy: If the effects of climate change are negligible where I live, they must be negligible globally.
Canada is experiencing climate change. According to the 2019 Canada’s Changing Climate Report, Canada has warmed by about 1.7 degrees C since 1948, close to double the global average, with the largest increases in the North, the Prairies, and northern BC. This report was conducted by Environment and Climate Change Canada (a federal agency) and is based on peer-reviewed literature.
Mr. Dyke: A meteorologist from Environment Canada forwarded me a Science Brief News report, dated March 2021, stating that due to the increased water temperature, models predicted that tropical storms would be bigger and possibly more frequent, and concluded that tropical storms would get bigger. However, included were quotes from the IPCC report stating that since 1900, no trend of increasing frequency or intensity has been observed. So, the models are not validated by empirical results.
Dr. X: Tropical storms are complicated, and the evidence on historical changes in storm frequency is equivocal. We would expect to see more damage from the largest storms, but not necessarily more storms overall. The historical record is not very reliable before the satellite era, because weaker storms may have been missed. This makes it harder to confirm trends.
Here’s what the IPCC said about tropical storms in its Special Report on the Ocean and Cryosphere in 2019:
The average intensity of tropical cyclones, the proportion of Category 4 and 5 tropical cyclones and the associated average precipitation rates are projected to increase for a 2 degree C global temperature rise above any baseline period (medium confidence). Rising mean sea levels will contribute to higher extreme sea levels associated with tropical cyclones (very high confidence). Coastal hazards will be exacerbated by an increase in the average intensity, magnitude of storm surge and precipitation rates of tropical cyclones. There are greater increases projected under RCP8.5 than under RCP2.6 from around mid-century to 2100 (medium confidence). There is low confidence in changes in the future frequency of tropical cyclones at the global scale.
Note the different confidence ranges, an example of the way IPCC reports are explicit about the strength of the evidence for each claim.
Mr. Dyke: Oceans have been rising at a rate of about 1 mm per year since 1860 and it is not increasing. In any case, these rates are very difficult to determine because continents rise and fall, and as temperatures change, the volume of water changes.
Dr. X: This is false, alas. Global mean sea level has been rising by about 3 mm per year since 1993, when global sea level could first be measured by satellites. The satellite measurements have global coverage and high precision, unlike earlier tide gauge measurements.
As temperatures rise, water expands. This is a major component of sea level rise. (Additional mass from glaciers and ice sheets is the other one). Recent work shows that sea level rise is accelerating.
Mr. Dyke: Susan Crockford, a zoologist at the University of Victoria who has been studying wildlife in the Arctic for thirty years, does not believe polar bears are in danger, and Inuit researchers agree. In fact, overall, their numbers are increasing.
Dr. X: Most scientists who study Arctic climate change think polar bears are in danger. Here’s a recent example. I’m not aware of any peer-reviewed studies showing that the number of polar bears is increasing. Can you point me to one? To be fair, I’m also not aware of studies showing that polar bear populations are decreasing. This doesn’t mean they aren’t threatened by climate change. It might mean that polar bears are hard to count accurately—or were, until recently, so it’s too soon to see a trend.
Mr. Dyke: Judith Curry, an American climatologist, has debunked many of the claims of climate activists and is horrified at the lack of rigor in so much climate research.
Dr. X: Based on my own experience, Judith Curry is a smart scientist, but can you give an example of an important scientific claim (not an activist claim) that she has shown to be false? Has she identified statements in IPCC reports that were not rigorously vetted? A comment on rigor: There is a vast difference between what counts as evidence in the geoscience community and what is accepted as evidence by the public at large.
Mr. Dyke: CO2 levels in the atmosphere have risen to about 400 ppm, higher than they have been in recent history. This has no effect on animal life, and greenhouses sometimes increase CO2 levels to 2000 ppm to encourage plant life.
Dr. X: The statement that high CO2 has no effect on animal life is true in the narrow sense that animals don’t suffer directly from breathing air with 420 ppm CO2 as opposed to 280 ppm CO2. But animals will suffer from other effects of increasing CO2, including warming and ocean acidification.
Some plants thrive under higher CO2 and others don’t. As CO2 levels change, so does the competitive balance among species. A recent Scientific American article (one of which I approve) summarizes the pros and cons. The broad claim that higher CO2 is on balance a good thing for plants or the humans who eat them is not supported. For example, there is evidence that many crops, including wheat, rice and soy, have fewer nutrients when grown in high-CO2 conditions.
Mr. Dyke: Millions of years ago CO2 levels were as high as 2000 ppm. Where did it go? It was consumed by plants and became one of the components of plant and animal life, and ended up captured as carboniferous rock, coal, oil, and natural gas, all of which abound. Once CO2 levels reach about 130 ppm, plants struggle to survive. That would be the end of life on earth. Is it possible that putting CO2 back into the atmosphere is a good thing, regardless of any effect on the temperature?
Dr. X: It is highly unlikely that adding CO2 to the atmosphere is a good thing, on balance. We are confident that levels of 500 ppm or higher are suboptimal for most natural systems, which for the past million years (until 1850) have seen CO2 concentrations between 200 and 280 ppm.
Mr. Dyke: History tells us that starting about 800 AD, the Vikings sailed across the North Atlantic in open boats and settled in Greenland. They raised crops and cattle. At about the same time, grapes were being grown in England to make wine. This was the Medieval Warm Period, well documented. About 1200 AD, the weather grew colder. By about 1600, the Vikings had been wiped out of Greenland by the Inuit, the cold, and the lack of support from home. About 1630, Samuel Pepys’ diary records bitterly cold winters, and the Thames froze. This was the Mini Ice Age. It has been warming ever since. The Roman Empire reached its peak at a time of very warm temperatures. In travels in Ireland, I visited the site of an ancient agrarian culture, the Ceide Fields, from about 5000 BC. It thrived during a period of very warm temperatures.
Dr. X: That some regional warming is a good thing doesn’t mean long-term global warming is a good thing. As far as we know, the Medieval Warm Period was largely confined to Europe and the North Atlantic. The global warming of recent decades has no precedent in the past 1000 years, probably much longer. Prolonged global warming of 2 degrees C or more will probably conform to the portrait in the IPCC reports.
Mr. Dyke: But let’s assume we have anthropogenic climate change and CO2 needs to be reduced. What would be the impact of net zero carbon? In the developed West, we might be able to achieve this with huge disruption to our economies and our environment. There is not enough land for the necessary windmills and solar panels to power our economy. (See Bill Gates on this.) Nuclear is an option, but the number of plants that need to be built in the next nine years (to reach 2030 targets) cannot be built in time and require huge amounts of concrete and steel. Electric cars would reduce smog but have their own environmental waste. (Note that coal can be burned very cleanly now, except for CO2.) Concrete and steel production? Huge emissions. Presumably, only flights to Climate Change Conferences would be permitted.
Dr. X: These subjects lie beyond my science expertise.
Speaking as a citizen, I’ll point out that we don’t know that the disruption to our economy would be huge. Note the dramatic fall in the cost of renewable energy and the number of jobs that could be created in clean energy. We must also acknowledge the economic costs of not reducing GHG emissions. Then we have an optimization problem, not a binary proposition.
I couldn’t find the Bill Gates quote about insufficient land for wind and solar. But a number of people have estimated the land area required to meet electricity needs. In the US, one estimate suggests we would need solar panels covering an area of 20,000 square miles, or about one-fifth the area of Arizona. Say we double this to 40,000 square miles to allow for electrification of new sectors such as transportation. This would be roughly the area of paved surfaces in the US. That’s a lot of land, but I don’t know that it is beyond the limits of human engineering
I may be underestimating the manufacturing footprint for so many solar panels. Perhaps Casey Handmer, who wrote an essay on solar power, could comment on this.
On climate scientists flying to too many conferences: Guilty as charged. But one of the few benefits of Covid-19 is that we’ve finally figured out how to work together virtually.
Mr. Dyke: What about the developing world? The progress made in these countries is due to cheap energy, and the cheapest energy is coal. To deny them access to fossil fuels is to send them back to the Stone Age. Nuclear power plants are technically challenging to build and operate. They require sophisticated systems of education, regulation, and quality assurance. Accidents happen in developed countries. Does anyone see nuclear power plants in Third World countries presenting the risk of terrorism, accidents, or the proliferation of nuclear weapons?
Dr. X: Again, speaking only as a citizen: I’ve read that in many places, solar power is now cheaper than coal per unit of energy produced, even before accounting for external costs of coal, in health risk and climate change, borne by the public. I agree that nuclear power, in the hands of the technologically unsophisticated, poses risks.
Mr. Dyke: The Chinese, Indians, and other Asian and African nations pay lip service to the efforts to control global warming in the hopes that money will flow to them, while they continue to invest in coal, oil, and gas infrastructure because they need to feed their people and develop as fast as they can. The Chinese of course are world leaders in the manufacture of solar panels, which they gleefully sell to the West.
Dr. X: I will venture only the patriotic comment that I’d like to see more solar panels made in the USA.
Mr. Dyke: According to Patricia Adams of Probe International, China is desperate to secure long-term supplies of oil and gas, hence its militarization of the South China Sea. China’s only secure form of energy is coal, which accounts for 58 percent of its consumption. China built 38.4 gigawatts of coal power last year and plans another 247 gigawatts. Chinese climate targets are pure propaganda.
Dr. X: Without commenting on the motives of China’s leaders, I will point out that wind and solar energy are inherently secure in countries with abundant wind and sunlight.
Mr. Dyke: Bjorn Lomborg, who accepts anthropogenic warming, states that even if all the Paris commitments were met, which they will not be, it would only affect global temperatures by a fraction of a degree. And in a list of existential threats to humans and to the planet, global warming does not even make the top ten.
Dr. X: A fraction of a degree compared to what? If the claim is that meeting the Paris commitments will lower global temperatures by only a fraction of a degree compared to not quite meeting those commitments, then it’s tautological. If the comparison is to doing no mitigation whatsoever, then the claim is probably false.
I avoid the term “existential threat” because it’s often used hyperbolically, as if the extinction of humans were imminent. If I were listing top threats to human well-being, however, as opposed to survival, global warming would be high on the list. I do think it’s appropriate to talk about existential threats to low-lying island nations inundated by sea level rise. The entire population could safely move elsewhere, but in some sense the nation would no longer exist.
Mr. Dyke: So why has the world gone crazy? Why do so many believe global warming is an existential threat? Nigel Lawson, former Chancellor of the Exchequer of the UK, says politicians love it. They cannot cure crime in the streets, poverty, homelessness, drug addiction, the potential for nuclear war, or prevent pandemics, but hey!! We will solve Global Warming! We will be heroes, and by the time we are shown to be wrong, or to have failed, we will be gone.
Dr. X: Speaking as a scientist: On the present emissions trajectory, climate scientists predict many changes that threaten human well-being, but these are not imminent threats to the survival of the species.
Speaking as a citizen: It is rational, although not necessarily common, for politicians to want to mitigate credible threats to human well-being.
Mr. Dyke: And why has it become so politicized? So many people on the Left, Obama, John Kerry, Al Gore, the American Guru of Global Warming Michael Mann, academics, and environmental activists, believe capitalism is running amok, causing inequity and all manner of social ills. The existential threat of global warming fits so well with their view of the world. Governments must take control. Most of them have forgotten that their livelihood depends on the taxes from people who mine, farm, manufacture, construct, and extract fossil fuels. Odd that the environment in the West is in better shape than it has been in centuries, and environmental degradation is most severe in former communist countries, where governments have been in control.
Dr. X: Now we come to the crux of the matter. Why, indeed, has climate science been politicized? Most geoscientists would prefer their work be judged on the scientific merits, independent of politics, but that’s become wishful thinking.
I see the politicization of climate science as a failure of communication. When we have pseudo-arguments about settled science, we miss the chance to have real arguments based on non-scientific values and evidence. By now, it’s largely a waste of time to argue about whether we should reduce greenhouse gas emissions. Of course we should reduce greenhouse gas emissions; the question is how fast, and by what means. Nevertheless, many are unconvinced.
I would ask the following question (as a citizen, not a scientist): Who has the motive and means to persuade intelligent people to believe scientific claims for which there is little or no evidence, while denying claims with abundant evidence? I can’t answer the question with precision, but some obvious candidates are fossil fuel companies, politicians, and media companies that monetize attention.
Some who doubt well-established science see themselves as defending core values related to the proper role of government, the balance between free and regulated markets, and the importance of different kinds of work. But denying the science is a logical error. It is not an affirmation of non-scientific values, but a needless distraction. This kind of error, as Mr. Dyke points out, is not confined to those on the right of the political spectrum.
Although Claire has not revealed my identity, I can confirm that I am not Michael Mann.
Mr. Dyke: Technically, we don’t know how to control the climate. If we did, politically I do not see the world agreeing to take whatever action might be required. And economically, the proposed solutions would be a catastrophe.
Dr. X: Broadly speaking, we know how to control the climate. Add GHGs to the atmosphere, and the Earth warms (among other changes). Remove GHGs, and it cools. Again, I am not convinced that cutting GHGs will be economically catastrophic compared to the alternative of unmitigated warming.
Mr. Dyke: The only action we should be taking is to make our economies strong enough to be able to adapt to whatever changes come our way.
This seems to be a claim that we should do nothing to limit climate change, regardless of our best understanding of how nature works. Reasonable people, I submit, would assess the evidence as best they can, then choose what seems to be an optimal balance of mitigation and adaptation measures. Compromise will be necessary, and solutions will be imperfect. But it isn’t a binary choice between mitigation and adaptation. We must do both.
I will close with some questions for climate skeptics. For the sake of the argument, let’s suppose you accept the science and conclude that a failure to mitigate GHGs will make the Earth less hospitable for present and future generations. What policies would you advocate? Would you support decentralized wind and solar energy production, and the end of fossil-fuel subsidies? What about government investment in a more robust and efficient electric grid? Would you pay out-of-work miners to cap methane leaks? In short, how can we mitigate GHGs with minimal cost and maximal benefits?
That, I think, is a discussion worth having.
Again, I warmly thank Mr. Dyke for joining this discussion and for his commendable openness.
I hope to follow with a final post about how to think about scientific uncertainty when considering large changes in how we generate energy.
Dr. X is a climate scientist who has spent more than two decades developing global climate and Earth system models.
From Claire: I’ve taken the minor liberty of adjusting Mr. Dyke’s spelling to conform to our Style Guide.