Both the blogosphere and the mainstream media have been abuzz with commentary blaming global warming for Hurricane Sandy and the associated deaths and devastation. Bloomberg BusinessWeek epitomizes this brand of journalism. Its magazine cover proclaims the culpability of global warming as an obvious fact:

Part of the thinking here is simply that certain aspects of the storm (lowest barometric pressure for a winter cyclone in the Northeast) and its consequences (worst flooding of the New York City subway system) are “unprecedented,” so what more proof do we need that our fuelish ways have dangerously loaded the climate dice to produce ever more terrible extremes?

After all, argues Climate Progress blogger Brad Johnston, quoting hockey stick inventor Michael Mann, “climate change is present in every single meteorological event.” Here’s Mann’s explanation:

The fact remains that there is 4 percent more water vapor – and associated additional moist energy – available both to power individual storms and to produce intense rainfall from them. Climate change is present in every single meteorological event, in that these events are occurring within a baseline atmospheric environment that has shifted in favor of more intense weather events.

Well sure, climate is average weather over a period of time, so as climate changes, so does the weather. But that tautology tells us nothing about how much — or even how — global warming influences any particular event. Moreover, if “climate change is present in every single meteorological event,” then it is also present in ”good” weather (however defined) as well as “bad.”

Anthony Watts makes this criticism on his indispensable blog, noting that as carbon dioxide (CO2) concentrations have risen, the frequency of hurricanes making landfall in the U.S. has declined.

The US Has Had 285 Hurricane Strikes Since 1850: ‘The U.S. has always been vulnerable to hurricanes. 86% of U.S. hurricane strikes occurred with CO2 below [NASA scientist James] Hansen’s safe level of 350 PPM.’

If there’s anything in this data at all, it looks like CO2 is preventing more US landfalling hurricanes.

Data Source: NOAA; Figure Source: Steve Goddard

Cato Institute climatologists Patrick Michaels and Chip Knappenberger put the point this way:

Global warming has to affect “the weather” in the United States, or anywhere else. Big deal. Changing the radiative properties of the atmosphere — which is what increasing carbon dioxide does — must alter the character of weather events as well as the climate. But how much? In reality, the amount of weather related to natural variability dramatically exceeds what is “added on” by global warming. This is obvious from a look at the “Climate Extremes Index” from the National Climatic Data Center …

Source: National Climate Data Center (Note: The graph above differs slightly from the one presented in Pat and Chip’s column because it incorporates NCDC’s tropical cyclone indicator.)

Michaels and Knappenberger go on to observe:

While it is true that this index has risen from a low point around 1970, it is also clear that it merely returned to values observed in the early 20th century. Did greenhouse gases raise the extremes index in the early 20th century? Obviously not.

Hurricanes are certainly less common in New York than in Florida or Louisiana, but if Sandy’s invasion of the Big Apple is evidence of global warming, then global warming has menaced the Empire State for centuries, because hurricanes have hit New York since before the industrial revolution.

Wikipedia has a List of New York Hurricanes going back to the 17th century. The strongest was the New England Hurricane of 1938, a category 3 storm that killed upwards of 600 people.

As I read the Wiki list, the following number of hurricanes have affected New York: 6 before 1800; 23 from 1800 to 1899; 11 from 1900 to 1949; 15 from 1950 to 1974; 21 from 1975 to 1999; and 19 from 2000 to the present (including Sandy). Each storm in the Wiki list is footnoted, usually with a link to the source referenced.

Lest anyone see a greenhouse “fingerprint” in the larger number of hurricanes since 1975, 16 were “remants” of tropical storms. In contrast, only one “remnant” is identified for 1950-1974 and none is identified for 1900-1949. No doubt New York experienced many hurricane remnants that were not identified as such before the advent of weather satellites and hurricane hunter aircraft.

Okay, but what about Sandy’s record-breaking storm surge — is that evidence global warming added extra oomph to the storm’s destructive power?

Anthony Watts posts an illuminating commentary by David Middleton, who compares Sandy’s estimated maximum storm surge with other hurricane surges in southern New England based on Donnelly et al., 2001. Middleton writes:

Hurricane Sandy’s unprecedented storm surge was likely surpassed in the New England hurricanes of 1635 and 1638. From 1635 through 1954, New England was hit by at least five hurricanes producing greater than 3 m storm surges in New England. Analysis of sediment cores led to the conclusion “that at least seven hurricanes of intensity sufficient to produce storm surge capable of overtopping the barrier beach (>3 m) at Succotash Marsh have made landfall in southern New England in the past 700 yr.” All seven of those storms occurred prior to 1960.

The early 1600s were the depth of the Little Ice Age, the coldest century of the past two millennia and possibly the coldest century since the cooling event of 8,200 years ago.

Anthony also posts a commentary by Caleb Shaw, who argues that the 11.2-foot storm surge from the 1821 Norfolk-Long Island Hurricane would likely have surpassed Sandy’s 13.8-foot surge had the same non-meteorological factors been present:

The people of the time reported a tide 13 feet above the ordinary high tide, but the best studies put the peak tide at 11.2 feet. Sandy reached 13.88 feet. . . .Simple arithmetic suggests the 1821 storm’s high water was 2.68 feet lower than Sandy’s. However the interesting thing about the 1821 storm is that it came barreling through at dead low tide. Tides in New York vary roughly 6 feet between low and high tides.

Therefore, to be fair, it seems you should add six feet to the 1821 storm, if you want to compare that storm with Sandy’s surge at high tide. This would increase the 1821 high water to 17.2 feet.

On top of that, you have to factor in the influence of the full moon during Sandy. That adds an extra foot to the high tide. Add an extra foot to the 1821 score and you have 18.2 feet.

Sandy was a category 1 hurricane before making landfall in the Northeast, which means many landfalling hurricanes, including some previous storms striking New York, had much higher wind speeds. What made Sandy a “superstorm” was the hurricane’s merging with a strong winter storm. MIT climatologist Kerry Emanuel calls Sandy a “hybrid” storm:

Hurricanes and winter storms are powered by completely different energy sources. The hurricane is powered by the evaporation of sea water. Winter storms are powered by horizontal temperature contrasts in the atmosphere. So hybrid storms are able to tap into both energy sources. That’s why they can be so powerful.

NASA scientist Roy Spencer provides a similar explanation:

It is basically the “perfect storm” scenario of the chance timing of a tropical cyclone merging with an extra-tropical winter-type storm. Without Hurricane Sandy off the coast, the strong trough over the eastern U.S. (caused by cold Canadian air plunging southward) would have still led to a nor’easter type storm forming somewhere along the east coast of the U.S. But since Hurricane Sandy just happens to be in the right place at the right time to merge with that cyclone, we are getting a “superstorm”.

This merger of systems makes the whole cyclone larger in geographical extent than it normally would be. And this is what will make the surface pressures so low at the center of the storm.

The immense area of the storm is also what enabled the winds to pile up huge masses of water into the big waves that pummeled the East Coast.

Is there a causal connection between global warming and the formation of hybrid storms? Not enough research has been done on this phenomenon to say one way or the other, Emanuel contends:

We don’t have very good theoretical or modeling guidance on how hybrid storms might be expected to change with climate. So this is a fancy way of saying my profession doesn’t know how hybrid storms will respond to climate [change]. I feel strongly about that. I think that anyone who says we do know that is not giving you a straight answer. We don’t know. Which is not to say that they are not going to be influenced by climate, it’s really to say honestly we don’t know. We haven’t studied them enough. It’s not because we can’t know, it is just that we don’t know.

But surely, the magnitude of the damage wrought by Sandy is evidence something is amiss with the global climate system, right? Actually, no, argues hurricane expert Roger Pielke, Jr. in a Wall Street Journal column.

In studying hurricanes, we can make rough comparisons over time by adjusting past losses to account for inflation and the growth of coastal communities. If Sandy causes $20 billion in damage (in 2012 dollars), it would rank as the 17th most damaging hurricane or tropical storm (out of 242) to hit the U.S. since 1900 — a significant event, but not close to the top 10. The Great Miami Hurricane of 1926 tops the list (according to estimates by the catastrophe-insurance provider ICAT), as it would cause $180 billion in damage if it were to strike today. Hurricane Katrina ranks fourth at $85 billion.

To put things into even starker perspective, consider that from August 1954 through August 1955, the East Coast saw three different storms make landfall — Carol, Hazel and Diane — that in 2012 each would have caused about twice as much damage as Sandy.

With respect to hurricane damages, the chief and as yet only discernible difference between recent and earlier decades is that ”There are more people and more wealth in harm’s way.” So there is an ‘anthropogenic’ component, but not the sort about which warmists complain. “Partly this [increase in damages] is due to local land-use policies, partly to incentives such as government-subsidized insurance, but mostly to the simple fact that people like being on the coast and near rivers,” Pielke, Jr. explains.

The upshot for policymakers? Since “even under the assumptions of the IPCC changes to energy policies wouldn’t have a discernible impact on future disasters for the better part of a century or more,” the “only strategies that will help us effectively prepare for future disasters are those that have succeeded in the past: strategic land use, structural protection, and effective forecasts, warnings and evacuations. That is the real lesson of Sandy.”

 New York Times environment blogger Andrew Revkin comes to a similar conclusion:

You can have this endless debate about, “Was this storm our fault?”  But the thing I’ve been trying to write on Dot Earth the last few days is that the impacts of this storm are 100 percent our fault. In other words, we make decisions every day as human beings about where to live, what kind of building codes, what kinds of subsidies for coastal insurance, and that’s where there’s no debate about the anthropogenic influence. The fact that the tunnels filled showed that we in New York City, New York State and this country didn’t make it a high priority to gird ourselves against a superstorm.

In a recent study published in Procedings of the National Academy of Sciences (PNAS), NASA scientist James Hansen and two colleagues find that whereas “extremely hot” summer weather ”practically did not exist” during 1951-1980, such weather affected between 4% and 13% of the Northern Hemisphere land area during 2006-2011. The researchers infer that human-caused global warming is “loading” the “climate dice” towards extreme heat anomalies. They conclude with a “high degree of confidence” that the 2003 European heat wave, the 2010 Russian heat wave, and the 2011 Texas-Oklahoma drought were a “consequence of global warming” and have (as Hansen put it in a recent op-ed) ”virtually no explanation other than climate change.”

In a recent post, I reviewed studies finding that the aforementioned anomalies were chiefly due to natural variability. In another post, I summarized an analysis by Patrick Michaels and Chip Knappenberger, who conclude that “the 2012 drought conditions, and every other [U.S.] drought that has come before, is the result of natural processes, not human greenhouse gas emissions.”

But what about the very hot weather afflicting much of the U.S. this summer? Greenhouse gas concentrations keep rising, heat spells are bound to become more frequent and severe as the world warms, and the National Oceanic and Atmospheric Administration (NOAA) reports that July 2012 was the hottest July ever in the U.S. instrumental record. Isn’t this summer what greenhouse warming “looks like“? What else could it be?

University of Alabama in Huntsville (UAH) climatologist John Christy addressed these questions last week in a two-part column. In Part 1, Christy argues that U.S. daily mean temperature (TMean) data, on which NOAA based its report, ”do not represent the deep atmosphere where the enhanced greenhouse effect should be detected, so making claims about causes is unwise.” A better measure of the greenhouse effect is daily maximum temperature (TMax), and TMax records set in the 1930s remain unbroken. In Part 2, Christy argues that Hansen’s 10% estimate of the portion of land affected by extreme heat during 2006-2011 shrinks down to 2.9% when anomalies are measured against a longer, more representative climate baseline. 

NOAA’s claim that July 2012 was the hottest July ever is based on daily mean temperature (TMean) data. TMean is the average of daytime maximum temperature and nighttime minimum temperature (TMax + TMin/2). Whereas TMax “represents the temperature of a well-mixed lower tropospheric layer, especially in summer,” TMin “can warm over time due to an increase in turbulent mixing” near the surface. Land use changes such as urbanization, agriculture, and forestry tend to disrupt the natural formation of a shallow layer of cool nighttime air. There has been a lot of population growth and development in the U.S. since 1980, the last year of Hansen’s baseline period. Not coincidentally, most of the surface warming in the U.S. during the past three decades has been in TMin rather than TMax (see second graph below).

The point? TMin warming is not primarily due to the accumulation of heat in the deep atmosphere (i.e. the greenhouse effect). Consequently, averaging TMin with TMax produces a composite (TMean) that inflates the appearance of the greenhouse effect.

Christy’s colleague Roy Spencer produced a chart of TMax using the same weather stations as NOAA. Spencer found that July 2012 was very hot, but not as hot as the summers of 1936 and 1934. More importantly, far more all-time TMax records were set in the 1930s than in any recent decade.

In contrast, about as many TMin records were set in recent years as in the 1930s.

Christy comments:

There has been a relatively steady rise in high TMin records (i.e. hot nights) which does not concur with TMax, and is further evidence that TMax and TMin are not measuring the same thing. They really are apples and oranges. As indicated above, TMin is a poor proxy for atmospheric heat content, and it inflicts this problem on the popular TMean temperature record which is then a poor proxy for greenhouse warming too.

Although TMax is a better proxy than TMin for the greenhouse effect, only satellites can provide “direct and robust” measurements of the heat content of the global atmosphere. UAH satellite data do show that the Earth has been in a long-term warming trend (+ 0.14°C per decade since November 1978). However, the data also show that July 2012 was not the hottest July in the 34-year satellite record either for the continental U.S., the Northern Hemisphere, or the world.

Christy finds two main weaknesses in Hansen’s study. First, it assumes that changes in TMean accurately represent the effect of extra greenhouse gases. Second, it assumes that the distribution (bell curve) of weather anomalies during single 30-year period (1951-1980) represents natural climate variability over the past 10,000 years or so.

As discussed above, TMean “misrepresents the response of the climate system to extra greenhouse gases.” So Christy uses TMax data to estimate trends in hot weather anomalies. In addition, he calculated the spatial extent of North Hemisphere extreme heat anomalies during 2006-2011 using both Hansen’s baseline (1951-1980) and a somewhat longer baseline that includes the 1930s and 1940s (1931-1980). Christy’s results are much less dramatic than Hansen’s.

In the figure above, the top line (black-filled circles) shows the percentage of the Northern Hemisphere land area that the Hansen team calculated to have experienced anomalously high heat during 2006-2011. The next line (gray-filled circles) assumes the same base period (1951-1980) for gauging anomalies, but uses TMax from the quality-controlled Berkeley Earth Surface Temperature (BEST) station data. Although the “correlation between the two is high,” the spatial coverage drops by more than half, ”from Hansen’s 6-year average of 12 percent to this analysis at 5 percent.”

The third line (open circles) gauges TMax anomalies in 2oo6-2011 against a 1931-1980 baseline. The result is that 2.9% of the Northern Hemisphere land area experienced extreme heat anomalies — about a quarter of the Hansen team’s results. “In other words,” says Christy, ”the results change quite a bit simply by widening the window back into a period with even less greenhouse forcing for an acceptable base-climate.”

The lowest line (open boxes) uses an 80-year baseline (1931-2010) to identify extreme hot weather anomalies during 2006-2011. In this case, only 1.3% of the land surface in 2006-2011 experienced anomalously high heat.

One might object that the 80-year baseline includes the most recent 30 years of greenhouse warming and, thus, masks the impact of greenhouse gas emissions on the ‘natural’ climate. However, excluding the most recent 30 years, as Hansen does, is question-begging – it assumes what Hansen sets out to prove, namely, that the current climate is outside the range of natural variability. That assumption conflicts with studies finding that the Northern Hemisphere was warmer than present for several decades during the Medieval Warm Period and Roman Warm Period and for thousands of years during Holocene Optimum. Christy asks:

What is an accurate expression of the statistics of the interglacial, non-greenhouse-enhanced climate? Or, what is the extent of anomalies that Mother Nature can achieve on her own for the “natural” climate system from one 30-year period to the next? I’ll bet the variations are much greater than depicted by 1951-1980 alone, so this choice by Hansen as the base climate is not broad enough. In the least, there should be no objection to using 1931-1980 as a reference-base for a non-enhanced-greenhouse climate.

During this week’s GOP presidential candidates debate in California, Texas Gov. Rick Perry made a statement about global warming that Mother Jones, the Huffington Post, the UK Guardian, and others condemn as “anti-science.” Asked by moderator John Harris of Politico “which scientists” are “most credible” in questioning “the idea that human activity is behind climate change,” Perry replied:

Well, I do agree that there is – the science is – is not settled on this. The idea that we would put Americans’ economy at – at- at jeopardy based on scientific theory that’s not settled yet, to me, is just – is nonsense. I mean, it – I mean – and I tell somebody, I said, just because you have a group of scientists that have stood up and said here is the fact, Galileo got outvoted for a spell. But the fact is, to put America’s economic future in jeopardy, asking us to cut back in areas that would have monstrous economic impact on this country is not good economics and I will suggest to you is not necessarily good science. Find out what the science truly is before you start putting the American economy in jeopardy.

The UK Guardian was quick to denigrate Perry’s answer:

It’s one thing to question the economic impact and legacy of current climate policy proposals – you would expect and wish for politicians to debate this – but for a politician to question the science in this way is striking. . . .Note how he studiously ignored the moderator’s well-crafted question: who exactly are these “Galileos” that you believe have so comprehensively cast doubt on the canon of climate science? Perry couldn’t – or wouldn’t – name them.

The Guardian makes a mountain out of a molehill. If Harris was so keen to know which climate scientists Perry finds most credible, he could have just restated the question. Perry was apparently more interested in making two basic points: (1) he does not view global warming as a warrant for imposing massive new regulatory burdens on the U.S. economy; (2) he is not impressed by appeals to an alleged “scientific consensus” because, after all, scientific issues not settled by counting heads.

The question Harris asked is bound to come up again and again in candidate forums, and it’s a bit of a loaded question at that. Alarmists would like us to believe that any human contribution to climate change constitutes a “planetary emergency” (Al Gore’s phrase) and, as such, justifies the imposition of cap-and-trade and other assaults on affordable energy. Hence, they would like nothing better than to trick opponents into arguing as if the case against cap-and-trade, or against EPA’s hijacking of climate policy, hinges on the implausible thesis that greenhouse gases do not have a greenhouse (warming) effect.

How then should presidential contenders respond to such questions?

Here’s how I would answer Harris’s question:

The premise of your question, If I’m not mistaken, is the notion, popularized by Al Gore, that any human contribution to climate change by definition constitutes a “planetary emergency” demanding urgent regulatory action. This is ideology, not science. The key scientific issue is not whether greenhouse gas emissions have a greenhouse effect but how sensitive Earth’s climate is to the ongoing rise in greenhouse gas concentrations. The sensitivity issue is far from being “settled.” You asked for names of credible scientists. Three who raise fundamental questions about the sensitivity assumptions driving the big, scary global warming forecasts are Richard Lindzen, Patrick Michaels, and Roy Spencer. The debate on climate sensitivity will likely be with us for some time. At this point, all I can say is that those who assume a highly sensitive climate have a hard time explaining why there’s been no net global warming over the past 14 years.

Much of what we hear about global warming is hype and scaremongering. If climate change is the dire peril some people claim it is, then why has there been no acceleration in sea-level rise over the past five decades? Why did heat-related mortality in the USA decline, decade-by-decade, from the mid-1960s to the late 1990s? Why has there been no long-term increase in hurricane-related economic damages once you adjust for increases in wealth, the consumer price index, and population? Why have total deaths and death rates related to extreme weather events declined by 93% and 98%, respectively, since the 1920s? Why has U.S. farm output increased dramatically over the past half century?

For more than two decades, the environmental movement has been pushing an ideology that might be called Kyotoism or, alternatively, Gorethodoxy. This is the view that global warming is a catastrophe in the making from which we can save ourselves only by waging the moral equivalent of war on affordable energy. The real catastrophe would be in enacting their agenda of cap-and-trade, energy taxes, and more subsidies for companies like Solyndra. Not even a prosperous America could afford to replace coal, oil, and natural gas with wind turbines, solar panels, and biofuel. We certainly cannot afford to do so in the current economic crisis.

UPDATE (September 14, 2011): 

On Monday, prolific energy scholar Rob Bradley excerpted most of my blog post at Masterresource.Org in a column titled “Andrew Dressler Challenges Rick Perry: How Should Perry Respond?” Dressler is a climatologist at Texas A&M. 

Science writer David Appell posted a comment on Bradley’s column, asserting: “It’s easy to refute Lewis.” So on Tuesday, I posted a column at Masterresource.Org responding to Appell’s comment. The column fleshes out the argument I presented above, in sound bite-sized chunks, at Globalwarming.Org.

I am happy to report that MIT physicist Richard Lindzen sent me an email outlining how he would discuss climate science within the space of a sound bite. I reproduce Dr. Lindzen’s comment below with his permission:

Virtually all scientists working on climate do agree that there has been a fraction of a degree of warming since the middle of the 19th century, that CO2 has been increasing, and that this should contribute something to the warming. However, the crucial question is whether the contribution is large enough to be of concern, and even the presidents of the National Academy of Sciences and the Royal Society agree that this is still unknown. Indeed, even if the increase in CO2 accounted for all of the observed warming, it would not imply a dangerous sensitivity. If the models on which alarm is based are correct then man has contributed several times more warming than has been observed. Modelers skirt this issue by claiming that aerosols have hidden the difference, but this is simply the invocation of fudge factor since the aerosol impact is unknown, and each model chooses a different value.