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.

If you follow global warming news at all, you’ve probably seen the NASA satellite images (above) many times. The images show the extent of Greenland surface ice melt on July 8 (left) and July 12 (right). In just a few days, the area of the ice sheet with surface melting increased from about 40% to 97%, including Summit Station, Greenland’s highest and coldest spot.

NASA took a drubbing from Patrick Michaels and Chip Knappenberger at World Climate Report (“Illiteracy at NASA“) for describing the ice melt as “unprecedented” in the title of the agency’s press release. The word literally means without precedent, and properly refers to events that are unique and never happened before. In reality, as one of NASA’s experts points out in the press release, over the past 10,000 years, such events have occurred about once every 150 years:

“Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” says Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data.

Equating ’rare yet periodic’ with ‘unprecedented’ is incorrect and misleading. “But apparently,” comment Michaels and Knappenberger, “when it comes to hyping anthropogenic global warming (or at least the inference thereto), redefining English words in order to garner more attention is a perfectly acceptable practice.” New York Times blogger Andrew Revkin also chided NASA for an “inaccurate headline” and the associated “hyperventilating coverage,” but for a different reason: NASA provided “fodder for those whose passion or job is largely aimed at spreading doubt about science pointing to consequential greenhouse-driven warming.”

Enough on the spin. Let’s examine the real issues: (1) Did anthropogenic global warming cause the extraordinary increase in surface melting between July 8 and July 12? (2) How worried should we be about Greenland’s potential impact on sea-level rise?

The answer to question (1) is that greenhouse warming does not appear to be the cause. Revkin links to a graph that shows similar melting events at Summit Station not only in 1889 but also in Medieval times, centuries before the advent of SUVs and coal-fired power plants.

NASA, moreover, ascribes the rapid expansion in surface ice melt to a high pressure blocking pattern, the same phenomenon that produced the recent heat wave and drought in the U.S. Midwest. NASA reports:

This extreme melt event coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland. The ridge was one of a series that has dominated Greenland’s weather since the end of May. “Each successive ridge has been stronger than the previous one,” said [Thomas] Mote [a climatologist at the University of Georgia]. This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later.

There is no known link between such blocking patterns and global climate change. It’s also worth noting that the dramatic surface ice melt began to reverse around July 14th. Greenland did not shift into a new climate regime.

If such events start to occur more frequently than once every 80-250 years, a global warming link would be more credible. As Prof Eric Wolff of the British Antarctic Survey told BBC News: “While this is very unusual, as always we cannot attribute any individual extreme event to climate change: We will have to wait and see if more such events occur in the next few years to understand its significance for both the climate and the health of the ice sheet.”

On to question (2): How much ice is Greenland shedding, and what are the implications for global sea-level rise? A study published in Science magazine in 2006 by Scott Luthcke of NASA and colleagues used satellite gravity measurements to estimate annual net ice loss in Greenland from 2003 to 2005. The researchers estimated that the ice sheet gained 55 gigatons per year from snowfall at higher elevations and lost 155 gigatons per year at lower elevations, yielding a net annual ice loss of 101 gigatons. That translates into an annual loss of 27 cubic miles of ice per year, or 2,700 cubic miles per century. Sounds huge — until you compare it to Greenland’s total ice mass. The Greenland Ice Sheet holds 706,000 cubic miles of ice. So at the 2003-2005 ice loss rate, Greenland will lose less than 4/10th of 1% of its ice mass in the 21st century. Apocalypse not.

Pat Michaels reviews a more recent gravity measurement study (Wu. et al. 2010, published in NatureGeoscience) that estimates ice mass balances in both Greenland and Antarctica from 2002 to 2008. Similar to the Luthcke study, the Wu team finds that Greenland’s net ice loss is 104 gigatons per year. They also estimate that Antarctica is losing 87 gigatons per year. What does it mean for sea-level rise? Pat comments:

It takes about 37.4 gigatons of ice loss to raise the global sea level 0.1 millimeter—four hundredths of an inch. In other words, ice loss from Greenland is currently contributing just over one-fourth of a millimeter of sea level rise per year, or one one-hundreth of an inch.  Antarctica’s contribution is just under one-fourth of a millimeter per year.  So together, these two regions—which contain 99% of all the land ice on earth—are losing ice at a rate which leads to an annual sea level rise of one half of one millimeter per year. This is equivalent to a bit less than 2 hundredths of an inch per year.  If this continues for the next 90 years, the total sea level rise contributed by Greenland and Antarctica by the year 2100 will amount to less than 2 inches.

Couple this with maybe 6-8 inches from the fact that the ocean rises with increasing temperatures, and 2-3 inches from melting of other land-based ice, and you get a sum total of about one foot of additional rise by century’s end.

An additional foot of sea level rise is less than a third the amount (“more than a meter“) forecast by a group of alarmist scientists calling themselves the “Copenhagan Consensus.” It is small potatoes compared to the 18-20 feet of sea-level rise Al Gore warned us about in An Inconvenient Truth. An additional foot of sea level rise is about twice the amount the world has experienced since 1880. There were surely costs associated with sea-level rise in the 20th century, but as a factor affecting public health and welfare it was so trivial most people never noticed. Our wealthier, more mobile, and more technologically advanced children’s children’s children should be able to adapt to 12 inches of sea-level rise and do just fine.

A favorite doomsday scenario of the anti-carbon crusade hypothesizes that global warming, by melting frozen Arctic soils on land and the seafloor, will release billions of tons of carbon locked up for thousands of years in permafrost. Climate havoc ensues: The newly exposed carbon oxidizes and becomes carbon dioxide (CO2), further enhancing the greenhouse effect. Worse, some of the organic carbon decomposes into methane, which, molecule for molecule, packs 21 times the global warming punch of CO2 over a 100-year time span and more than 100 times the CO2-warming effect over a 20-year period.

The fear, in short, is that mankind is fast approaching a “tipping point” whereby outgassing CO2 and methane cause more warming, which melts more permafrost, which releases even more CO2 and methane, which pushes global temperatures up to catastrophic levels.

In a popular Youtube video, scientists flare outgassing methane from a frozen pond in Fairbanks, Alaska. A photo of the pond, with methane bubbling up through holes in the ice, appears in the marquee for this post. Are we approaching the End of Days?

New York Times science blogger Andrew Revkin ain’t buying it (“Methane Time Bomb in Arctic Seas – Apocalyplse Not,” 14 Dec. 2011), nor does his colleague, science reporter Justin Gillis (“Artic Methane: Is Catastrophe Imminent?“ 20 Dec. 2011).

Revkin excerpts a recent paper on the subject published by the American Geophysical Union:

[T]he authors found that roughly 1 meter of the subsurface permafrost thawed in the past 25 years, adding to the 25 meters of already thawed soil. Forecasting the expected future permafrost thaw, the authors found that even under the most extreme climatic scenario tested this thawed soil growth will not exceed 10 meters by 2100 or 50 meters by the turn of the next millennium. The authors note that the bulk of the methane stores in the east Siberian shelf are trapped roughly 200 meters below the seafloor . . .

Revkin also checked in with Ed Dlugokencky, a top methane researcher at NOAA’s Earth System Research Laboratory, who told him:

[B]ased on what we see in the atmosphere, there is no evidence of substantial increases in methane emissions from the Arctic in the past 20 years.

Gillis addresses the most alarming aspect of the ‘methane time bomb’ scenario — the risk that global warming will melt billions of tons of frozen methane formations known as hydrates and clathrates on the seafloor. He reports:

While examples can already be found of warmer ocean currents that are apparently destabilizing such deposits—for example, at this site off Spitsbergen, an island in the Svalbard archipelago in the Arctic—the scientists explained that a pervasive ocean warming sufficient to destabilize a lot of methane hydrates would almost certainly take thousands of years.

And even if that happened, many scientists say that the methane released would largely be consumed in the sea (by bacteria that specialize in eating methane) and would not reach the atmosphere. That is what seems to be happening off Svalbard.

“I think it’s just dead wrong to talk about ‘Arctic Armageddon,’ ” said William S. Reeburgh, an emeritus scientist at the University of California, Irvine, who spent decades studying such matters and says the likely consumption of methane within the ocean should not be underestimated. “Most of this methane is never going to see the atmosphere.”

And now for my two cents. The Arctic was warmer than present for thousands of years during both the Holocene Climate Optimum (roughly 9,000 to 5,000 years ago) and the Last Interglacial Period (roughly 130,000 to 100,000 years ago).

The chart below, from the IPCC’s Fourth Assessment Report (chapter 6, p. 462), shows that most places above 30N experienced greater-than-present warmth during the Holocene Optimum.

Pat Michaels and Chip Knappenberger,* writing in World Climate Report, note that the IPCC chart does not show the full extent of Holocene Optimum Arctic warmth. The IPCC’s data for North Eurasia comes from a paper by UCLA’s Glen McDonald. Chip and Pat quote the paper’s abstract:

Radiocarbon-dated macrofossils are used to document Holocene treeline history across northern Russia (including Siberia). Boreal forest development in this region commenced by 10,000 yr B.P. Over most of Russia, forest advanced to or near the current arctic coastline between 9000 and 7000 yr B.P. and retreated to its present position by between 4000 and 3000 yr B.P. Forest establishment and retreat was roughly synchronous across most of northern Russia. Treeline advance on the Kola Peninsula, however, appears to have occurred later than in other regions. During the period of maximum forest extension, the mean July temperatures along the northern coastline of Russia may have been 2.5° to 7.0°C warmer than modern. The development of forest and expansion of treeline likely reflects a number of complimentary environmental conditions, including heightened summer insolation, the demise of Eurasian ice sheets, reduced sea-ice cover, greater continentality with eustatically lower sea level, and extreme Arctic penetration of warm North Atlantic waters. The late Holocene retreat of Eurasian treeline coincides with declining summer insolation, cooling arctic waters, and neoglaciation.

Average July temperatures along the Russian coastline “may have been 2.5° to 7.0°C warmer than modern” for two millennia. Such warmth was associated with ”extreme Arctic penetration of warm North Atlantic waters.” Yet the greenhouse effect did not gallop away. Either clathrates did not melt en masse, or the bugs ate most of the methane before it could reach the atmosphere.

Turning to the Last Interglacial Period, Michaels and Knappenberger, in a separate post, review a study by the Circum-Arctic PaleoEnvironments (CAPE) project. The CAPE researchers conclude that summer air temperatures were “4-5°C above present over most Arctic lands” for thousands of years.

So if Arctic warmth were capable of detonating a methane time bomb, it should have happened during the Last Interglacial. What do the data tell us?

Vostok ice core data do show a correlation between changes in global temperature and atmospheric levels of both CO2 and methane. However, despite the sustained Arctic warmth of the Last Interglacial, there was no de-stabilizing, self-perpetuating spike in atmospheric methane levels. Global temperatures largely determined methane levels, not the other way around.

Atmospheric data going back 420,000 years indicate that the climate is more stable than alarmists assume. Even greater-than-present Arctic warmth sustained over thousands of years did not turn the permafrost or the seafloor into a climate-disrupting methane bomb.

* Pat and Chip have been covering the permafrost scare since 2007 (here, here, and here).

Richard Morrison and Marc Scribner welcome back long-lost co-host Michelle Minton to Episode 101 of the LibertyWeek podcast. Among other issues, we discuss the IPCC’s latest attempt to muzzle its own advisory scientists (segment begins approximately 10 minutes in).