David Siegel’s ten claims about climate

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1. Global warming and extreme weather

There are numerous studies that have identified links between extreme weather events and global warming. According to these studies higher temperatures cause more intense hurricanes, heavier rainfalls and flooding, increased conditions for wildfires and dangerous heat waves. Global warming loads the weather dice to make these extreme events more likely. Counter to this evidence Siegel wrote the following statement:

“Weather is not climate. There are no studies showing a conclusive link between global warming and increased frequency or intensity of storms, droughts, floods, cold or heat waves.” (Claim by David Siegel.)

To support this point Siegel linked to an article about hurricanes and tropical cyclones, on the NOAA website. (If you read further down in Siegel’s article, you may have noticed a contradiction. David says that NOAA is one of the sources he doesn’t trust. That the NOAA is not to be listened to. This sort of tactic, cherry picking pieces and rejecting the whole, is a red flag of the type mentioned earlier.)

The article Siegel linked to does not dispute the fact that global warming affects tropical cyclones. All weather is affected by global warming. The first conclusion it lists is that it is not yet possible to determine a detectable impact of climate change. This conclusions are that:

It is not yet possible to determine a detectable impact of global warming on Atlantic hurricane or global tropical cyclone activity.

impact of global warming on Atlantic hurricane or global tropical cyclone activity. It is likely that by the end of this century, human-caused warming will result in more intense tropical cyclones, and an increase in frequency in some ocean basins.

Associated rainfall is likely to increase by 10 to 15% over this century.

Just how much global warming will change tropical cyclone frequency and strength over time is an area of active research. However, there is evidence that the increase in strength has already started to happen, associated with increasing ocean temperatures. There is general agreement among experts that there are likely to be more high category (Category 4 and 5) storms as the world continues to warm, and hurricanes will produce much heavier rainfall than in the past. Professor Kerry Emanuel from MIT advised us there is already evidence indicating that in the western North Pacific and in the North Atlantic, hurricanes will reach peak intensity further north. He added that there is less consensus about the frequency of weak hurricanes, which cause much less damage. Kerry Emmanuel said:

“Because the frequency of high intensity (Cat 4 and 5) storms is expected to increase, and because these dominate the total damage done by hurricanes even though they are relatively rare, we expect surge and wind damage from hurricanes to increase in many places. We also expect increased incidence of freshwater flooding from torrential hurricane rains.”

Cyclones are fueled by warm water, provided the wind shear is low. As the seas get warmer, the intensity of tropical cyclones will continue to increase. Events like Hurricane Patricia are a warning sign of what is to come. And the combined effect of stronger storms and rising seas means double trouble, as explained by scientist Peter Jacobs in a video:

Siegel talks about studies showing a “conclusive link” between global warming and storms, droughts, floods, cold or heat waves. Because extreme events are, almost by definition, rare events, it is difficult to assess the relative contribution of global warming. As scientists wrote in a Letter in Nature, following the extreme heat wave in Europe in 2003:

“It is an ill-posed question whether the 2003 heatwave was caused, in a simple deterministic sense, by a modification of the external influences on climate — for example, increasing concentrations of greenhouse gases in the atmosphere — because almost any such weather event might have occurred by chance in an unmodified climate.”

What scientific research can and does show, is the likelihood of extreme events being exacerbated by human-caused warming. This can be done by, for example, assessing the likelihood of such events occurring with and without global warming. In a supplement to the Bulletin of the American Meteorological Society (BAMS), scientists reported that human-caused global warming very likely played a role in the following extreme events in 2012 and 2013:

The Californian drought

The Australian record heat

Extreme rainfall in north eastern Colorado

The New Zealand drought

The heat waves in Korea and Japan

The hot summer in central eastern China

Severe precipitation in northern India

The hot, dry summer in western Europe.

To understand how extreme events might have changed, one can also refer to IPCC reports, which identify an increase in heatwaves and heavy precipitation. From Chapter 10 of the AR5 WGI document:

“It is likely that human influence has substantially increased the probability of occurrence of heatwaves in some locations.”

and

“there is medium confidence that anthropogenic forcing has contributed to a global-scale intensification of heavy precipitation over the second half of the 20th century”

2. How much warming?

Scientists have found multiple fingerprints that point to human activity as the cause of the current increase in temperatures. Changes in the types of carbon in the air, the small, but measured parts per million drop in oxygen concentrations, no natural explanations for the change in temperature, the enhanced greenhouse effect seen from satellites, the list goes on. These many lines of empirical evidence are what make scientists so confident in their conclusion that we are causing global warming. Yet Siegel wrote:

“Natural variation in weather and climate is tremendous. Most of what people call “global warming” is natural. The earth is warming, but not quickly, not much, and not lately.” (Claim by David Siegel.)

Natural variation in weather is largely defined by the climate of a region. Some parts of the world have a lot of variability in weather. Other places not so much. Siegel’s claim that global warming is natural is simply not supported by the evidence. The dominant cause is the very large increase in atmospheric carbon dioxide, a greenhouse gas. Global mean surface temperature is already around 1 °C higher than it was in the 1850s, as shown in the chart below. The chart is based on data from the Hadley Centre, UK Met Office and shows the change in temperature from 1850 to the present, from the average over the 30 years 1851 to 1880.

Data source: UK Met Office Hadley Centre

3. Understanding climate, using models

For the third of his ten points, David Siegel, wrote as if he was putting himself forward as some sort of expert in climate models. On the contrary, his article indicates that he does not understand climate models (or the concept of scientific uncertainty). He wrote:

“There is tremendous uncertainty as to how the climate really works. Climate models are not yet skillful; predictions are unresolved.” (Claim by David Siegel.)

You might ask, why trust climate models? The answer is that they provide insight into climate, and what we can expect as the world warms. The claim that models are not yet skillful is certainly incorrect. A model being skillful does not mean that the model is 100% “right”, it means that a model can tell us something about a system that we wouldn’t otherwise know, or be able to understand. There are plenty of examples of climate models being skillful. As early as the 1960s, models predicted that the stratosphere would cool in response to increasing atmospheric greenhouse gases (Manabe & Wetherald 1967). This has indeed been observed (Thomson & Solomon 2005). Predictions, in the late 1980s, of future warming in response to increasing anthropogenic emissions have also been shown to have been skillful (Hargreaves 2010). Predictions in the 1990s of the response to the Pinatubo eruption were, again, skillful (Hansen et al 1992). The response to the solar cycle shows skill.

The Director of the Goddard Institute of Space Science, Dr Gavin Schmidt, explains in a Ted Talk video why climate models are skillful.

4. It’s not the sun

David Siegel’s fourth wrong claim was that global temperature is more highly correlated with solar radiation. That is incorrect. It is currently the second most popular myth listed at SkepticalScience.com. Siegel wrote:

“New research shows fluctuations in energy from the sun correlate very strongly with changes in earth’s temperature, better than CO2 levels.” (Claim by David Siegel.)

Not only does this suffer from the correlation doesn’t imply causation problem, it’s not correct. In the last 50 years there has been a slight reduction in solar insolation while temperatures have continued to rise. Furthermore, changes in solar forcing over the 20th century are small compared to changes in anthropogenic forcings. To argue that the sun has been the dominant driver of 20th century warming suggests that our climate is very sensitive to changes in solar forcing, while being very insensitive to changes in anthropogenic forcings. This is not a logically consistent position.

In his section on “smoking guns”, Siegel refers to papers authored by Willie Soon, whose work claiming “it’s the sun” is seriously flawed. The latest scientific report from the IPCC states there is high confidence that recent warming is not from the sun:

There is high confidence that changes in total solar irradiance have not contributed to the increase in global mean surface temperature over the period 1986 to 2008, based on direct satellite measurements of total solar irradiance. There is medium confidence that the 11-year cycle of solar variability influences decadal climate fluctuations in some regions. No robust association between changes in cosmic rays and cloudiness has been identified.

The science shows that, contrary to what David Siegel wrote, solar forcing had a small negative influence on climate between 1980 and 2011. The chart below is from Chapter 8 of the IPCC AR5 WG1 report. It lists the forcings that have acted on climate between 1980 and 2011. The forcings from human activity, anthropogenic forcings, are shown at the top, and the main natural forcing, solar irradiance, is shown at the bottom. Almost all the forcing is positive (as can be seen from the axis at the bottom of the chart). Changes in solar irradiance over this period were a negative forcing, counteracting the human-caused forcings to a small extent. That’s because the amount of energy coming from the sun over this period was slightly less than in previous periods, so the sun didn’t warm the planet as much as it had been in earlier decades.

Linear trend in anthropogenic, natural and total forcing for the indicated time periods. The uncertainty ranges (5–95% confidence range) are combined from uncertainties in the forcing values (from Table 8.6) and the uncertainties in selection of time period. Monte Carlo simulations were performed to derive uncertainties in the forcing based on ranges given in Table 8.6 and linear trends in forcing. The sensitivity to time periods has been derived from changing the time periods by ±2 years. Source: Figure 8.19 from the IPCC AR5 WG1 report

5. Carbon dioxide as the climate control knob

Atmospheric carbon dioxide is the biggest control knob of climate. More of it and the world heats up. When it drops, the world cools. It is well-mixed in the atmosphere and lasts a very long time before being removed through the carbon cycle.

As his fifth objection to mainstream science, David Siegel wrongly claimed that carbon dioxide has little impact on climate:

“CO2 has very little to do with it. All the decarbonization we can do isn’t going to change the climate much.” (Claim by David Siegel.)

It’s hard not to describe this simply as climate science denial. The influence of CO2 as a greenhouse gas is well understood and goes back to Svante Arrhenius in 1896. Although Arrhenius’ original work suggested that our climate is more sensitive than we currently think, our current understanding is still remarkably similar to what he presented. Based on paleoclimate studies, equilibrium climate sensitivity (how much the planet will eventually warm after doubling atmospheric CO2) is likely to be between 2.2 °C and 4.8 °C. In the short to medium term, the IPCC AR5 report estimates that the planet will warm by between 1.5 and 4 °C with a doubling of CO2. And it will continue to warm more if atmospheric CO2 continues to increase. At a meeting in Ringberg in March this year, many of the talks from experts suggested that, in fact, temperatures will probably increase by more than 2 °C, with a doubling of CO2. The higher range of sensitivity estimates (4.0 °C and higher) are not any less likely than the lower estimates (around 2 °C), but would have much worse impacts.

Given that we’re on track to double atmospheric CO2 by the middle of this century, suggesting that decarbonization would not have much effect is wrong. Stopping CO2 emissions won’t cool the planet in the short to medium term, but it will limit the amount of global warming we will suffer, and reduce the pace of warming.

In 2009, renowned glaciologist and climate researcher, Professor Richard Alley gave the Bjerknes Lecture at the AGU Fall Meeting. He described in some detail how scientists know, based on evidence of climates in the distant past as well as the present, that CO2 is the climate control knob:

6. CO2 as pollution

This sixth objection of David Siegel is commonly raised by people who, for mostly ideological reasons, do not want to take action to mitigate climate change. He objected to the word “pollution”:

“There is no such thing as “carbon pollution.” Carbon dioxide is coming out of your nose right now; it is not a poisonous gas. CO2 concentrations in previous eras have been many times higher than they are today.” (Claim by David Siegel.)

It is indeed true that CO2 concentrations in previous eras have been much higher than today, but not at a time when humans, and most other currently present species, were also on the Earth. It’s also true that CO2 plays an important role in both keeping the surface warmer that it would be in the absence of an atmosphere (the Greenhouse effect) and in the planetary life cycle (photosynthesis requires CO2). Pollution, however, is simply the introduction of substances (foreign, or naturally occurring) into the natural environment that could cause adverse changes. Elevated levels of carbon dioxide, such as commonly encountered indoors or in heavy traffic, have been shown to adversely affect human cognition and decision-making. Claiming that there is no such thing as “carbon pollution” ignores the harm caused by rapid changes to climate from increasing carbon dioxide in the air.

7. What causes the sea to rise?

David Siegel predicts that seas will continue to rise, but he wrongly claims that it’s not from greenhouse warming. He doesn’t indicate what he thinks will cause the sea level to go up. He doesn’t say what he thinks will cause ice sheets to melt and water to expand. He wrote:

“Sea level will probably continue to rise, naturally and slowly. Researchers have found no link between CO2 and sea level.” (Claim by David Siegel.)

Whether warming or sea level rise at any time is from natural forces or human activity, there is always a cause. Saying “natural” means little unless you can say what natural (or other) force is causing the change.

Sea level rise is associated with thermal expansion as the oceans warm, and the addition of extra water through the melting of land ice. This is one of the more concerning outcomes of climate change. Between 140 and 220 million people live on land that may be below sea level by the end of the century if CO2 emissions continue on their current trend, and three times that number may be affected. An interactive tool was published in the New York Times last year, which shows the countries most at risk from rising sea levels. This is a grave concern not just because of the need to relocate millions of people, it has serious ramifications for trade, commerce, and security.

Jonathan Gregory is the lead author of the study David Siegel used as evidence for his claim that there is no link between CO2 and sea level. Professor Gregory told us that Siegel misrepresents their work, and said:

“According to our estimates, the contribution from thermal expansion of the ocean *did* increase in rate, because of the increasing anthropogenic warming (mostly due to CO2), but this was partly offset by the cooling due to a large number of volcanic eruptions in recent decades.”

Jonathan Gregory added that sea levels would not have risen as quickly, if not for human-caused warming:

“the implication is that, without CO2 forcing, the rate of sea level rise would have decreased during the 20th century, rather than weakly increasing.”

The seas are rising at an increasing rate. In 2011, John Church and Neil White (who were co-authors of the Gregory study cited by David Siegel) analysed the sea level rise from the late 19th to the early 21st century. They found that the linear trend from 1900 to 2009 was 1.7 ± 0.2 mm a year. For the period 1993 to 2009 they estimated the rise to be 3.2 ± 0.4 mm a year. The CU Sea Level Research Group at the University of Colorado report the latest trend from 1993 to 2015 as being 3.3 ± 0.4 mm a year.

This is not a huge rate of increase. However, seas are expected to rise a lot faster and higher as the ice sheets in Antarctica and Greenland melt more rapidly. The rise is unlikely to be gradual. There will be decades when sea level will rise very quickly, and others when it will not rise as fast. Many sea level experts regard as conservative the IPCC projections of 0.5 to 1 metre by 2100 under the highest emission scenario (Chapter 13 in the IPCC AR5 WG1 report). A paper published in 2014, reported an assessment by 90 experts from 18 countries. The range of estimates from these experts were that sea level will rise from between 0.7 meters and 1.2 metres by the end of this century with unmitigated warming (RCP8.5), and two to three metres within two hundred years. The amount will depend on how quickly we add CO2 to the air, and how quickly the ice sheets melt. A paper recently published in Nature by Golledge et al, found that if we don’t constrain greenhouse gas emissions, sea level could rise by up to three metres (almost ten feet) in just two hundred years. From the abstract:

“…substantial Antarctic ice loss can be prevented only by limiting greenhouse gas emissions to RCP 2.6 levels. Higher-emissions scenarios lead to ice loss from Antarctic that will raise sea level by 0.6–3 metres by the year 2300. Our results imply that greenhouse gas emissions in the next few decades will strongly influence the long-term contribution of the Antarctic ice sheet to global sea level.”

RCP’s are the representative concentration pathways used in modeling studies for climate. We have gone beyond being able to achieve the lowest emissions pathway, RCP 2.6, by curbing CO2 emissions. To achieve RCP 2.6, we would most likely have to somehow remove CO2 from the air, using geo-engineering.

8. The Arctic is warming, ice is melting, threatening wildlife

In his eighth objection to science, Siegel refers to the situation in the Arctic, and polar bear numbers:

Yes, there is natural variation of weather and climate in the Arctic. The bigger impact over time will be from human-caused global warming. (Siegel’s first link is not to a science website, but to a blog that rejects mainstream science. The article discussed is a 2010 paper about the onset of ice breakup in Hudson Bay.)

The Arctic is warming faster than most of the rest of the world. This is as expected by climate science, and is known as polar amplification. Andy Lee Robinson has been illustrating the melting of summer sea ice over recent decades. His latest is shown below.

David Siegel links to an article in Canadian Geographic about polar bears. The article is nuanced, and doesn’t support what he implies, that global warming won’t impact wildlife in the Arctic. From the article, about how some polar bear populations have not declined in recent years:

News like this leaves climate-change deniers crowing from the rooftops. But a closer look reveals that everything may not be quite so sunny. “Some populations appear to be doing OK now, but what’s frightening is what might happen in the very near future,” says wildlife biologist Lily Peacock, who has worked with polar bears for the Government of Nunavut and the U.S. Geological Survey. “All indications are that the future does not look bright.” While population trends might appear stable, she says, “we’re picking up declines in body condition that are really frightening.” Scientists have shown a direct correlation between warm years and skinny bears. Even more distressing, one study predicted that 40 to 73 percent of pregnant females could fail to deliver healthy cubs if ice breakup happens one month earlier than in the 1990s. Polar bears are long-lived animals that reproduce slowly; counting the number of animals that are alive today might not paint an accurate picture.

Global warming won’t just have an impact on polar bears. It will affect one of our major food sources, wild fisheries. Scientists have been examining just how global warming will affect fisheries in the Arctic, pooling their expertise and knowledge. For example, through the FIMAGLOW project involving Norway, Iceland, Denmark and Sweden. (You can download the 2014 report here.)

9. Changes in the world’s oceans: warming and acidification

This penultimate of the ten objections by David Siegel makes a claim that is contrary to scientific evidence about the world’s oceans and marine life:

“No one has shown any damage to reef or marine systems. Additional man-made CO2 will not likely harm oceans, reef systems, or marine life. Fish are mostly threatened by people, who eat them.” (Claim by David Siegel)

In this claim, David Siegel ignores the impact of warming oceans. This year there is yet another major coral bleaching event underway. Bleaching events will happen more frequently as global warming increases. Corals can recover from mild bleaching events. However when they are severe, they can cause permanent damage to reefs. The latest chart from NOAA’s coral reef watch shows large areas of oceans that are on the highest alert.

Source: NOAA Coral Reef Watch

It’s not just events like coral bleaching as seas warm, Siegel ignores another threat caused by CO2 emissions: ocean acidification. Under normal circumstances, when the oceans warm they release CO2. Carbon dioxide dissolves in water more easily as the water cools. However, because atmospheric CO2 is increasing so quickly, the effect of the partial pressure outweighs that of temperature, and the oceans have absorbed about ⅓ of the extra CO2 we have put in the air since industrialisation. If not for that, the world would be warming even more quickly than it is.

This absorption of CO2 causes the pH of the oceans to drop. Some marine species are sensitive to pH. This includes many corals and shellfish. Professor of Marine Science at the University of Queensland, Ove Hoegh-Guldberg tells us:

“Consequently, this is pretty much an open and shut case. We are also continuing to create a situation in the world’s oceans that is unprecedented (in hundreds of millions of years of time), and which is already rapidly overwhelming physiological and genetic responses of marine organisms and processes. Evolution needs time to act — which is not happening faster in the case of ocean warming and acidification. Given the fundamental importance of ocean chemistry to life on earth, rapid changes of this scale are of great concern to anyone who understands this issue.”

10. The IPCC, United Nations and the Grand-Daddy of all Conspiracy Theories

In the final of his ten main objections, Siegel resorts to the “climate conspiracy” theory — that climate science is politics not science. He wrote:

The Intergovernmental Panel on Climate Change and others are pursuing a political agenda and a PR campaign, not scientific inquiry. There’s a tremendous amount of trickery going on under the surface*. (Claim by David Siegel.)

Siegel doesn’t link to any scientific report about this supposed “trickery”. Instead he links to a YouTube video by Richard Lindzen. Richard Lindzen used to be a climate scientist at MIT. These days, rather than publish research, he speaks at events run by organisations that oppose efforts to reduce global warming.

The claim that the IPCC is political is one of the misleading tenets of the “climate conspiracy” theories that circulate around the Internet. In the United States and Australia, climate change has been politicised in a manner different to that in most other countries.

The Intergovernmental Panel on Climate Change (IPCC) is a scientific body, under the auspices of the United Nations. It was established by the United Nations and the World Meteorological Agency in 1988, after governments became very concerned about how humans are changing the world’s climates. The IPCC has a very small staff complement and itself does not conduct any research. It relies on hundreds of scientists from around the world volunteering their time to prepare it’s reports. The IPCC reports are based on a compilation of scientific, technical and socio-economic information, which is relevant to climate change.

IPCC scientific and technical reports are written by people who are active researchers in the relevant subject matter. The report on the Physical Science Basis of Climate Change is prepared by Working Group I (WGI). A typical chapter will have two or three co-ordinating lead authors, 10 lead authors or more, and more than 20 contributing authors from around the world. Each chapter describes and references the findings from hundreds of published scientific papers. Before the final report is released, it is carefully reviewed by scientific experts as well as by external reviewers. The most recent WG1 report has 14 chapters, and the preparation involved:

209 Lead Authors

50 Review Editors from 39 countries

More than 600 Contributing Authors from 32 countries

Examining and citing more than 9,200 scientific publications

Analysing more than 2 million gigabytes of numerical data from climate model simulations, and

Considering 31,422 comments from 800 Expert Reviewers from 46 countries and 26 Governments, which were in turn reviewed by experts in the relevant fields.

The scientific report has been scrutinised by scientists, world leaders, government agencies, science journalists, and probably tens of thousands of people around the world. To imagine that all these people have collaborated in some sort of “climate coverup” without anyone noticing, is inconceivable.

It will be obvious to readers that, because the scientific report has been accepted by the 193 member countries, it can hardly be described as “political”. The member nations of the UN span the political spectrum and include government structures ranging from western-style democracies to totalitarian regimes. Climate change is something that politicians the world over would much rather not to have to deal with. Actions to mitigate climate change aren’t automatic vote-winners, except among people who understand the critical importance of climate policies.

The Summary for Policy Makers (SPM) needs to be accepted by representatives of the various governments, but this is not the case for the main scientific report. The process by which the SPM is finalised involves sessions whereby government representatives from around the world meet with scientists, to discuss the content and agree on final edits. To a great extent, the meeting where governments review the Summary for Policy-Makers is a word-smithing exercise, as can be seen by the list of edits and comparisons between the penultimate and final documents.

Either a conspiracy involving thousands of people has been foiled by a lone web design author, or David Siegel has made a foolish claim with no basis in reality.

Science, heresy and critical thinking

At the beginning of his article, David Siegel asks:

What is your position on the climate-change debate? What would it take to change your mind?

In our experience, most people who are motivated to reject climate science are not likely to change their mind. Rather than be swayed by scientific evidence, they decide that the data must be fudged, and that none of the thousands of scientific experts in disciplines related to climate can be “trusted”. They attempt to rationalise the irrational, arguing it must be a decades-long conspiracy of gigantic world-wide proportions.

After summarising his ten objections to mainstream climate science, David Siegel asked:

Could this possibly be right? Is it heresy, or critical thinking — or both?

We have demonstrated that no, David Siegel couldn’t possibly be right. His article is not heresy. The subject is science, not religion. There is no “immutable truth” in science. Knowledge is developed by evidence and rational explanation, which as evidence accumulates over time becomes accepted scientific theory.

Nor was David Siegel’s article an example of critical thinking. Instead, you can regard it as a fairly typical example of climate science denial, involving logical fallacies, cherry-picked data, fake experts and other telltale techniques, the same techniques and climate myths that are replicated on other “climate conspiracy” blogs on the Internet.