***************** College, University of ****************
MSc ******************************* programme
Year : 1 : Course Module : Climate Change
Reading Task : 6th October 2009
Read : Michaels, P.J. (2009) : “Global Warming and Climate Change”.
In : Cato Handbook for Policymakers (ed. D. Boaz, 7th edition). Cato Institute, p. 475-485.
Available from :-
1) How does he explain the observed periods of warming in the IPCC record?
Michaels states : “human activity has been a contributor since 1975.”
He expresses the view that a period of warming that he has identified between roughly between 1910 and 1945 was entirely due to “natural” causes : changes in solar activity. He identifies a second period of warming between roughly 1975 and 1998 as having a “clear “human” signature”, although he attributes “minority” of that second period of warming to “natural” causes.
2) What is his explanation of why global warming seems to have stopped?
Michaels attributes the lack of Global Warming since 1998 as due to a “compensatory cooling” after the strong El Nino temperatures of 1998, followed by changes in tropical ocean temperatures, as moderated by El Nino cycling, and low solar activity.
3) When does he think warming might restart and why?
Michaels suggests that the El Nino cycling and the solar activity may both turn around, which would “accelerate a warming trend”.
He also refers to the work of Noel Keenlyside ( Keenlyside N.S. et al. (2008) ), which suggests that Global Warming “may not resume until the middle of next decade”. The basis for these assertions are the work done to study the North Atlantic and south Pacific “multidecadal” oscillations.
4) What are the implications of this for our understanding of future projections?
Michaels claims that there has been “no net change in the earth’s average surface temperature in the last 11 years”, even though the figure he refers to, 45.2, shows a continuing upwards trend.
Michaels then enlists the work of Keenlyside to round up 11 years to 20 years, without any justification in the basis of the experiential data.
He then seeks to undermine confidence in the computer modelling of future projections of Climate Change, which he says do not allow for 20 years without warming.
5) What should politicians therefore do?
Michaels states in his initial summary : “Congress should (*) pass no legislation restricting emissions of carbon dioxide, (*) repeal current ethanol mandates, and (*) inform the public about how little climate change would be prevented by proposed legislation.”
In the text of the article, he suggests that because global warming takes a break, the politicians have time for the development of technologies that can lower carbon dioxide emissions to the atmosphere.
Michaels also says “Drastic action is unwarranted at this time.” and urges caution.
6) What other evidence is often used to show warming and how does he seek to undermine it?
Scientists studying the Arctic regions, which includes the Greenland area, continue to report increased “meltdown” : meaning increases in ice and snow melt, including increased glacier flow, increased ice shelf break-up and increased iceberg calving.
The Intergovernmental Panel on Climate Change reports in Chapter 4 of the Working Group 1 papers for the 2007 Fourth Assessment Report “Recent decreases in ice mass are correlated with rising surface air temperatures. This is especially true for the region north of 65°N, where temperatures have increased by about twice the global average from 1965 to 2005.” (IPCC 2007a).
This evidence strongly suggests that not only are Arctic and Greenland regional atmospheric and ocean temperatures rising, but that globally, warming is also taking place, as inevitably, heat travels.
Michaels proceeds to selectively report from the Greenland evidence, claiming that “The notion that Greenland’s temperatures are particularly unusual at this juncture is simply untrue…The data clearly demonstrate that the average temperature for the most recent decade is hardly unusual.” (Michaels P.J. (2009)).
He goes on to admit that there has been recorded evidence of Arctic sea ice decline over the years at the summer minimum since 1979, but discounts this evidence, claiming that the temperatures in the Arctic in the late 1970s were the coldest in the area since the 1920s.
Michaels asserts that “about half” the contraction of Arctic sea ice extent from 1979 to today “represents a return to more normal conditions for the 20th century”. He does admit that “The warming of the most recent years has resulted in another contraction to far below normal, compared to the last century.”, but he discounts this, by trying to normalise the condition. He conjectures that Arctic sea ice was “almost certainly” contracted or even completely absent “for millennia after the end of the last ice age” due to elevated temperatures in the region. He notes that the Arctic sea ice returned, so there was no “catastrophic loss of Greenland’s ice.”
Michaels uses this conjecture about absent Arctic sea ice in the period after the last ice age to challenge the theory that current contraction of Arctic sea ice could result in a permanent loss.
Michaels moves into the territory of discussing the projections and evidence of more and/or more intense tropical cyclones, majoring on the hurricane basin of the Caribbean Sea. He dismisses these projections on the basis of the work of Thomas Knutson, although the quote that he uses actually talks about the ability to detect increases in frequency and/or intensity.
The paper that he references (Knutson (2008)) says this in the abstract : “Here we assess…changes in large-scale climate that are projected to occur by the end of the twenty-first century…and find that Atlantic hurricane and tropical storm frequencies are reduced. At the same time, near-storm rainfall rates increase substantially. Our results do not support the notion of large increasing trends in either tropical storm or hurricane frequency driven by increases in atmospheric greenhouse-gas concentrations.”
Michaels almost correctly reports this when he writes “It is noteworthy that Knutson’s most recent work now calculates that the number of Atlantic tropical storms and hurricanes will decrease with global warming.” But he doesn’t get it quite right. The issue is that Knutson says “Our results do not support the notion of large increasing trends in either tropical storm or hurricane frequency driven by increases in atmospheric greenhouse-gas concentrations.” which is not quite the same thing. Atmospheric increases in greenhouse gas concentrations do not mean that all regions of the world will experience warming, or even the same levels of warming.
Then Michaels writes this : “In recent decades, as the surface temperature has warmed, the frequency of these storms has dropped in both the eastern North Pacific and Southern oceans.” But placing this information here could be misleading, as it is not related to what the Knutson report says, as it is discussing different areas of ocean. What Knutson says : “Increasing sea surface temperatures in the tropical Atlantic Ocean and measures of Atlantic hurricane activity have been reported to be strongly correlated since at least 1950.”
Michaels considers sea level rises later on in the article. He notes the projected rise in sea level, but discounts its significance. He makes reference to the projections that show that the Greenland ice cap could melt under high levels of Carbon Dioxide emissions, but he claims that this couldn’t possibly happen because :-
(a) He implies that Carbon Dioxide levels in the atmosphere couldn’t remain high with the italicised phrase “that concentration is maintained for 2,000 years.” and the sentence “Clearly, no one can possibly project the energy future of our society 100 years from today, much less 1,000 years.” He does not admit that Carbon Dioxide levels could stabilise at a very much higher level than they are today, even if the sources of emissions ceased operating.
(b) He cites the conclusion from the IPCC 2007 Fourth Assessment Report that sudden, rapid ice loss from Greenland is not possible.
(c) He hints that since society’s future use of energy (Fossil Fuels) cannot be properly projected, that atmospheric concentrations of Carbon Dioxide are not going to rise as high as the computer model that shows Greenland ice melting rapidly. “Clearly, no one can possibly project the energy future of our society 100 years from today, much less 1,000 years.”
7) Why does he think warming will be modest?
Michaels attributes most of the Greenhouse Effect to water vapour, without justification : “Water vapor…is in fact currently responsible for keeping the earth’s surface temperature nearly 30 degrees Centigrade warmer than it would be if there were none.”
He says that the effect of Carbon Dioxide acting on its own as a greenhouse gas would not have much effect : “If carbon dioxide were acting alone, the rise in surface temperature expected this century would be a little more than 1 degree Fahrenheit.” He does not give the source for this assertion, nor quantify the basis of any calculations he may have made.
However, he does include a chart from IPCC 2007 with a trend line showing 0.5 degrees Centigrade warming in 30 years, which would equate to 1.667 degrees Centigrade over 100 years, which would equate to 1.667 * 9 / 5 = 3 degrees Fahrenheit.
He says that the Carbon Dioxide-induced Global Warming will raise the temperature of the oceans and increase the water vapour rising from the surface of the oceans which will give added warming, as water vapour is a Greenhouse Gas.
Michaels then says this : “If, for any reason, warming stops for 20 years (it has already stopped for 11), the ‘‘feedback’’ effect between carbon dioxide and water vapor will also be delayed, as the ocean does not warm up instantaneously. This effect will be further delayed, resulting in less warming than was anticipated, at least in the first half of this century.”
Here he makes two basic mistakes and wraps himself in knots by his own logic.
a. He admits that there is a delay between rising concentrations of Greenhouse Gas in the atmosphere and global warming, owing to the fact that the ocean does not warm up instantaneously. What he neglects to do is reflect on the fact that current global warming we have measured must be subject to this delay, and that we may be looking at warming in the last few years that relate to changes in Greenhouse Gas from several decades ago as the warming effects have worked their way through the Earth system. This also means that there we are locked into further warming because of the current levels of Greenhouse Gas in the atmosphere. Since levels of Greenhouse Gas have not reduced, he is not justified in supposing : “If…warming stops for 20 years…” The recent low levels of warming relate to changes in various parts of the Earth system that were triggered by increases of Greenhouse Gas some decades ago. We know that increases in Greenhouse Gas have continued since that time, so more warming is inevitable.
b. Michaels states that increased global warming, caused by increased atmospheric Carbon Dioxide levels, causes more water vapour to rise from the oceans, and that this is a Greenhouse Gas itself, which causes warming. The rise in water vapour levels cannot be divorced from the rise in Carbon Dioxide levels, and the warming from water vapour increases cannot be divorced from warming due to increased Carbon Dioxide levels. When Michaels says “If, for any reason, warming stops for 20 years…the ‘‘feedback’’ effect between carbon dioxide and water vapor will also be delayed…”, but he has here made a basic tautological error : the warming is caused partly by the feedback effect, and cannot be considered separately from it.
8. What policy response does he suggest?
He suggests that “capital…would best be invested in the future”, but does not suggest in which way this investment should be done. He also urges caution in policies responding to Climate Change. He also recommends that the U. S. Congress communicate the information he writes about to “our citizens, despite disconnections between perceptions of climate change and climate reality”.
Read : Smith, D.M., Cusack, S., Colman, A.W., Folland, C.K., Harris, G.R. and Murphy, J.M. (2007). “Improved Surface Temperature Prediction for the Coming Decade from a Global Climate Model”. Science 317: 796-799 [DOI: 10.1126/science.1139540].
Answer the following questions [from the Abstract and first 3 paragraphs] :-
1) What was the problem with previous climate model projections?
Previous climate models took no account of “internal generated natural variability” in their predictions.
In other words, “unforced natural changes in the climate system such as El Nino”, create variability and cyclic changes that need to be modelled to provide more accurate projections.
2) What does their new system do that is improved ?
The new system predicts both internal variability and external forcings.
The new modeling system forecasts surface temperature with substantially improved skill throughout a decade”.
3) What do their results show?
“Our system predicts that internal variability will partially offset the anthropogenic global warming signal for the next few years. However, climate will continue to warm, with at least half of the years after 2009 predicted to exceed the warmest year currently on record.”
4) Why are we particularly interested in projections for the next decade?
The next decade is a “key planning horizon for infrastructure upgrades, insurance, energy policy, and business development.”
5) What are the main sources of internal climate variability?
The paper indicates that in the timeframe of a decade, the climate will be dominated by “internal variability”, that is, changes influenced by some parts of the Earth system on others. The natural changes that would show the most influence would be instances of El Nino cycling, fluctuations in the ocean “heat pump” circulation, and “anomalies of ocean heat content”, as hotter and colder water in the ocean mass move around between warmer and cooler areas of the Earth, accentuating the local variations.
6) What does the DePreSys model take into account that other models don’t?
The DePreSys modeling looks at the temperatures of the atmosphere and the ocean in order to work out from their amplitude where they fall in the likely range of short timescale variation; where they are likely to be in relation to the underlying average. The model also takes into account “plausible changes” in man-made Greenhouse Gas emissions and aerosols. It also takes into account likely solar irradiance changes and volcanic effects on aerosol content in the air.
7) How are they assessing the accuracy of the DePreSys model?
The researchers assessed the accuracy of the DePreSys model by running hindcasts along the time line starting in 1982, going by season.
What other model are they comparing it to? What is different about this model?
The DePreSys model is compared to the output from the NoAssim model, which is similar but does not take internal variability into account.
9) How good are the DePreSys and NoAssim hindcasts?
“We found that global anomalies (25) of annual mean surface temperature (Ts) were predicted with significantly more skill by DePreSys than by NoAssim throughout the range of the hindcasts.”
For the 5 year means, the accuracy was much better.
Can you use the results of the Smith et al (2007) study to counter some of Michaels’ (2009) arguments?
Michaels says : “So given the lack of warming since 1998, and projections for little or no warming until the middle of the next decade, there is no scientifically credible model for future warming.”
However, the Smith et al paper shows that the usual global climate models have been validated – when they are enhanced to include internal variability, they provide a much better projection skill.
Smith et al say : “We present a new modeling system that predicts both internal variability and externally forced changes and hence forecasts surface temperature with substantially improved skill throughout a decade, both globally and in many regions.”
Michaels says : “Most future projections for atmospheric carbon dioxide…predict constant rates of warming, once that warming is established.”
Smith et al. say : “Our system predicts that internal variability will partially offset the anthropogenic global warming signal for the next few years. However, climate will continue to warm, with at least half of the years after 2009 predicted to exceed the warmest year currently on record.”
Michaels says : “…there has been no net change in the earth’s average surface temperature in the last 11 years, as shown in the IPCC history (see Figure 45.2).” and “current indications are that warming may not resume until the middle of the next decade”
Smith et al. say : “Our system predicts that internal variability will partially offset the anthropogenic global warming signal for the next few years. However, climate will continue to warm,
with at least half of the years [in the next decade] after 2009 predicted to exceed the warmest year currently on record.
More problems with Michaels
Michaels mishandles the accumulation of Carbon Dioxide in the amosphere : “It has long been known that atmospheric carbon dioxide must build up at an ever-increasing (‘‘exponential’’) rate in order to simply support a constant rate of warming. Most future projections for atmospheric carbon dioxide indeed make this assumption. As a result, they tend to predict constant rates of warming, once that warming is established.”
In order to have an accumulation of Carbon Dioxide in the atmosphere it is merely necessary to have more Carbon Dioxide entering the atmosphere than leaving it. This could be a result of increased anthropogenic (man-made) emissions, but it could also be a result of “collapsing Carbon sinks” – as global warming takes effect it may well prevent parts of the Earth system from absorbing so much Carbon Dioxide out of the atmosphere.
Also, it is not necessary to have an ever-increasing rate of build-up of Carbon Dioxide in the atmosphere to raise the average global temperature. It is merely necessary to have more Carbon Dioxide in the air than previously. Michaels implies that he does not accept the long residence times of Carbon Dioxide in the atmosphere when he states in italics “that concentration is maintained for 2,000 years.” The Global Carbon Cycle processes mean that Carbon Dioxide can enter and exit the atmosphere many times from different parts of the Earth system before it is sequestered permanently outside the atmosphere. The Carbon Dioxide we are emitting today will continue to have an effect in the atmosphere for a long time, as it cycles in and out of soils, plants, oceans.
Michaels misunderstands the difference between Global Cooling effects and Global Warming.
He notes that after the El Nino spike in 1998 there were a few years of “compensatory cooling”. This cooling happened immediately following the very hot year of 1998.
But we have already discussed that Global Warming has a time lag between Carbon Dioxide rising in the atmosphere and the warming effect to be monitored. Even Michaels admits that there is a time delay between Greenhouse Gas build-up and warming effects.
So how can the “compensatory cooling” after the 1998 El Nino happen immediately ? The answer to this is that events like El Nino involve “ocean overturning”, in other words, the major heat sink, the ocean, convects, and cooler water comes to the surface. Since the air responds quickly to this, the air temperatures cool and we see immediate cooling.
However, the oceans as a whole are still warmer, and this eventually results in overall warmer air temperatures, maybe after years.
The same kind of immediate cooling effect is seen when large volcanoes erupt – it is thought because particles from the eruptions form reflective clouds high up in the atmosphere – deflecting more of the sun’s light than usual. This has an immediate effect of cooling air temperatures at the surface that last for a year or so. However, this is not a reversal of the underlying warming trend.
Michaels P.J. (2009)
Michaels, P.J. (2009) : “Global Warming and Climate Change”.
Cato Handbook for Policymakers (ed. D. Boaz, 7th edition). Cato Institute, p. 475-485.
Keenlyside N.S. (2008)
Keenlyside, N.S., and others. ‘‘Advancing Decadal-Scale Climate Prediction in the North Atlantic Sector.’’ Nature 453 (2008).
Nature 453, 84-88 (1 May 2008) | doi:10.1038/nature06921; Letter
The climate of the North Atlantic region exhibits fluctuations on decadal timescales that have large societal consequences. Prominent examples include hurricane activity in the Atlantic, and surface-temperature and rainfall variations over North America, Europe and northern Africa. Although these multidecadal variations are potentially predictable if the current state of the ocean is known, the lack of subsurface ocean observations that constrain this state has been a limiting factor for realizing the full skill potential of such predictions. Here we apply a simple approach—that uses only sea surface temperature (SST) observations—to partly overcome this difficulty and perform retrospective decadal predictions with a climate model. Skill is improved significantly relative to predictions made with incomplete knowledge of the ocean state, particularly in the North Atlantic and tropical Pacific oceans. Thus these results point towards the possibility of routine decadal climate predictions. Using this method, and by considering both internal natural climate variations and projected future anthropogenic forcing, we make the following forecast: over the next decade, the current Atlantic meridional overturning circulation will weaken to its long-term mean; moreover, North Atlantic SST and European and North American surface temperatures will cool slightly, whereas tropical Pacific SST will remain almost unchanged. Our results suggest that global surface temperature may not increase over the next decade, as natural climate variations in the North Atlantic and tropical Pacific temporarily offset the projected anthropogenic warming.
Wikipedia : Greenland Ice Sheethttp://en.wikipedia.org/wiki/Greenland_ice_sheet
Nature Geoscience 1, 359 – 364 (2008)
Published online: 18 May 2008 | doi:10.1038/ngeo202
Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions
Thomas R. Knutson, Joseph J. Sirutis, Stephen T. Garner, Gabriel A. Vecchi & Isaac M. Held
Increasing sea surface temperatures in the tropical Atlantic Ocean and measures of Atlantic hurricane activity have been reported to be strongly correlated since at least 1950, raising concerns that future greenhouse-gas-induced warming could lead to pronounced increases in hurricane activity. Models that explicitly simulate hurricanes are needed to study the influence of warming ocean temperatures on Atlantic hurricane activity, complementing empirical approaches. Our regional climate model of the Atlantic basin reproduces the observed rise in hurricane counts between 1980 and 2006, along with much of the interannual variability, when forced with observed sea surface temperatures and atmospheric conditions7. Here we assess, in our model system, the changes in large-scale climate that are projected to occur by the end of the twenty-first century by an ensemble of global climate models, and find that Atlantic hurricane and tropical storm frequencies are reduced. At the same time, near-storm rainfall rates increase substantially. Our results do not support the notion of large increasing trends in either tropical storm or hurricane frequency driven by increases in atmospheric greenhouse-gas concentrations.