The link between heat waves and global warming

In Saturday's Globe and Mail, Rex Murphy had yet another obtuse column speculating about global cooling, spurred by Toronto's cool, wet summer. While the errors in Murphy's supposedly ironic columns have not quite reached the level of George Will, in which a full-on intervention with the editorial board of the Washington Post now appears necessary, someone at the Globe and Mail could at least casually pull him aside and say "cut it out".

In this case, forget Mr. Murphy's apparent blindness to the constant flow of science and reporting on evidence for warming, nor the news that the combination of the decades-long warming trend and a developing El Nino event may make the next year one of the warmest, if not the warmest, year in the recorded history of the planet.

He doesn't appear to have even been reading or watching the national news. While his home and my hometown of Toronto has been cool and wet, Vancouver and western Canada have been in the midst of an unprecedented heat wave.

Fires burn throughout the BC interior. Water restrictions have placed in the Fraser Valley. On Saturday afternoon, Vancouver-ites put down the Globe and Mail to watch an impromptu lightning show upstage the planned Celebration of Light fireworks show (the photo shows the calm after the storm). That's right a thunderstorm here in placid, temperate Vancouver.

What's happening? On Sunday, I was asked the classic question "Is it global warming?" by a reporter from the local CBC affiliate.

I responded, as any climate scientist would, with a variation of Michael Tobis's old favourite: "no individual event can be attributed directly to climate change".

Yes, this the kind of weather we expect to see more frequently in the future. It won't happen every summer. And when it does happen, it won't happen everywhere. There will certainly be many summers when one part of the continent, say Vancouver, experiences typical "global warming" weather and another, say Toronto, experience old-fashioned cool summer, thanks to how the general warming trend affects upper-level atmospheric flow.

The "is it global warming?" question is bound to arise again and again over the next year. The answer is always going to be the same. Whether it is next year, ten years from now, or thirty years from now, we will not be able to definitively state with 100% certainty that a warm summer or a heat wave is due solely to climate change. That's the nature of this multifactorial beast known as the climate system.

What we will be able to say thirty years from now is that we should have spent more time trying to slow the warming trend, rather than arguing about the noise.

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Newspapers in the future

"We're not in it to make money" is sadly prophetic.

Hat tip to Jennifer Jacquet

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El Nino and the likelihood of mass coral bleaching

The seasonal forecasting system recently developed by NOAA Coral Reef Watch suggests that coral reefs in the Caribbean and in part of the central equatorial Pacific (the Line Islands, including Kiritimati or "Christmas Island") are at risk of coral bleaching in the coming months due to warm ocean temperatures. The forecast is due to the seeming return of El Nino in the Pacific.

The word from the NOAA Climate Prediction Center is that El Nino conditions are expected to prevail though the winter. Climate buffs can "see" the El Nino development in maps of sea surface temperature anomalies (warm water in the central and eastern Pacific) the thermocline (deepening in the eastern Pacific, meaning less upwelling off of South America) and sea surface height (the wind reversal on the equator means higher water in the central and eastern Pacific).

Not all El Nino events are created equal, and the models currently disagree on the current trajectory. This is especially important to remember when predicting the effect that El Nino conditions may have on other parts of the planet, what we luddites call "teleconnections". For example, a terrific paper by Kim et al. in Science demonstrated clear differences between the effect of "central pacific warming" and "eastern pacific warming" - which can both be classified as an El Nino event, depending what metric is applied - on ocean temperatures and hurricane tracks in the Caribbean.

One silver lining: For people living in the central Pacific, especially the parched islands of the southern Gilberts (Kiribati) Islands like Arorae, the development of El Nino conditions hopefully also means an end to the two-year drought that has claimed many of the coconut trees.

UPDATE: More on the Caribbean bleaching threat here

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Beneficial biofuels

A policy forum in this week's Science outlines the types of biofuel that could actually lead to net reductions in greenhouse gas emissions and have other societal or environmental benefits. The paper argues that current methods of growing energy-intensive biofuel crops (like corn in the US) on existing agricultural land and/or clearing land for biofuel crops (like palm oil in SE Asia) are clearly unacceptable, but that not all biofuels are inherently evil.

Here's their list of the potentially beneficial biofuels, for those without a subscription to Science:

Perennial plants grown on degraded lands abandoned for agricultural use

The two keys here are: i) using land that has not been storing large amounts of carbon, so clearing the land will not release that carbon, and ii) using land is not at all part of an existing or planned future production system so that biofuel production does not have a cascading effect on food production

Crop residues

This includes residues beyond what should be left on the field to regenerate the soil.

Sustainably harvested wood and forest residues

There is a lot of leftover from forest clearing and from pulp and paper production.

Double crops and mixed cropping systems

Fall or winter biofuel crops could be grown after the harvest of the traditional summer crops ("double" crops). This would eliminate the need to clear land and release carbon in order to grow biofuel crops. Winter or off-season cover crops are good for the soil anyway. And [the paper asserts that] biofuels grown as double crops could avoid the problem of competing for land with food production. This argument is debatable; one could also argue that we could increase double cropping to decrease land needs for food production.

Municipal and industrial wastes

Solid waste could be turned into liquid fuels. This would actually be a good solution in island nations where disposal is difficult.

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The challenge of agreeing on degrees

Andy Revkin has a nice short summary of the wisdom, or lack thereof, of pledging to avoid climate warming of 2 deg C or any other threshold beyond which climate disaster looms.

The problem is that not only is there no one firm threshold, but that even if there were, there is no reason to think we could agree on it. Yes, the uncertainty in scientific predictions is part of the problem. But the real issue is that there is no such thing as a good climate and a bad climate.

Vulnerability to climate warming varies not only between communities and ecosystems, but also between different people in any one community and different species or groups of species in any one ecosystem. Beyond that, there is an important are too often neglected difference between the perceived and actual vulnerability to climate change. Your conclusion about the limits of acceptable warming comes is determined not by how you or your community will be affected by climate warming, but how you think you or your community will be affected by climate warming, and how you think you or your community can respond.

Even for a system as vulnerable to changes in climate and ocean chemistry as coral reefs, the line is hard to draw. From my recent paper on committed warming:

The overall results of this study can provide insight into the level of atmospheric greenhouse gas concentrations required to avoid degradation of coral reef ecosystems from frequent mass coral bleaching, a proposed definition of “dangerous anthropogenic interference” in the climate system [39]. Specific recommendations about future greenhouse gas emissions pathways and/or atmospheric stabilization levels require normative judgments about the acceptable damages to coral reefs and the metrics for characterizing those damages. A comparison of the results from the key scenarios in this study does, however, present an envelope of possible climate futures for the world’s coral reefs, presuming that the models realistically represent the response of the climate system to external forcing.

Science can give guidance on the impacts of climate change and, from that, provide some general recommendations on what level of warming might be acceptable, given different assumptions. That's a key to all science. The results depend on the assumptions. When you hear that 2 deg C is the maximum "acceptable" warming, you need to ask what are the assumptions that went into defining "acceptable". And because we will not all agree on those assumptions, we will not all agree that 2 deg C, or 1 deg C, or 1.349 deg C is the threshold beyond which danger lurks.

What we're left with is a value judgment. In this case, the 2 deg C threshold is a convenient backstop, the sort of nice round number that works in policy discussions.

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Mixing mitigation and adaptation at the G8 summit

The climate change discussions at the G8 Summit have been a blank canvas upon which media outlets and commentators can project their judgments on the state of climate change policy. Is the story the agreement on a 2 deg C threshold? The lack of agreement with China and India? The refusal of Russia and Canada to pledge their own countries to an 80% reduction in GHG emissions by 2050? The disagreement over the baseline year for calculating emissions cuts?

Many of the more thoughtful articles have focused on the efforts to negotiate with developing nations on adaptation and development issues (that's a broken Kiribati seawall in the photo). The Globe and Mail, for example, ran a frontpage story entitled “Obama bends to bring emerging nations on side” complete with an unsubtle full fold photo of the back of US President’s rapidly graying head (a welcome to the world of climate change policy?).

The G8 leaders have pledged to help developing countries meet costs associate with reducing emissions. The reporting and (at least some of) the actual G8 discussion was mixing two quite different issues. First, how and how much to help emerging economies like China and India now responsible for a large fraction of the world’s greenhouse gas emissions reduce those emissions without slowing their development. Second, how to help developing countries more vulnerable to climate disasters adapt to climate change.

These are not the same things, and they will require different policies and different pots of money. The first is more about trade policy, setting environmental standards, etc. The second is more about international aid. We need to help countries like Kiribati or Mali, adapt to climate change far more than we need to help those countries reduce greenhouse gas emissions.

Neither task will be easy. Most policy discussions implicitly assume that getting the emerging economies like China to slow, stabilize or reverse emissions growth will be harder than helping the Kiribatis and the Malis adapt to climate change. The assumption comes in large part from ignorance of the hands-on, day-to-day challenge of international aid projects, especially those aimed at the often nebulous goal of increasing the adaptability of a different society to outside pressures, whether climate change, other environmental change, or global trade. In the end, we may discover that bringing China into an emissions policy is actually far easier than deciding whether, how, where and when to build sea walls in Kiribati.

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Climate change deal from the G8 summit?

[UPDATED POST]. The G8 has agreed on limiting warming to 2 deg C... but not on the emissions target that would limit warming to 2 deg C. Canada continues to fudge with the baseline year for calculating emissions change, an important issue given the rise in emissions since 1990

Coverage and criticism of the failure to reach a consensus on climate policy at international meetings like the G8 summits tend to focus, for good reason, on emissions reductions. The lede from the NY Times:

As President Obama arrived for three days of meetings with other international leaders, negotiators dropped a proposal that would have committed the world to reducing greenhouse gas emissions by 50 percent by midcentury and industrialized countries to slashing their emissions by 80 percent.

On top of emissions reductions, any post-Kyoto agreement, or any side agreement between individual nations like the US and China, will include funding for climate change adaptation in the developing world. As difficult as it will be to reach a global agreement on emissions reductions, it may actually be even more difficult to reach an agreement on funding for adaptation.

The emissions targets are promises in the politically-distant future; Canadians, for one, have seen how a promise of emission reductions can go for naught if there are no serious penalties tied to those targets. The funding for climate change adaptation in the developing world. on the other hand, is real money that comes out of existing budgets and shorter-term forecasts. And a system for adaptation funding is ripe for abuse, as happens with international aid.

First and foremost, we need to work on the emissions reductions policy. But let's not assume that agreeing on how and how much to funding adaptation will be easy.

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Abuse of science and logic by the National Corn Growers Association

The National Corn Growers Association released a report arguing that there is no connection between the use of nitrogen fertilizers on corn in the Midwestern US and the seasonal “Dead Zone” in the Gulf of Mexico.

There is no point mincing words about what this “analytical white paper”. It is the corn equivalent of irrational climate change skepticism. This is one truly shoddy piece of work. I encourage others in the scientific community to respond either independently or to append the critique offered here.

First, let’s review the actual science.

The “dead zone” in question, discussed many times before on this blog, is generated most summers on the continental shelf of the northern Gulf of Mexico. Nutrients originating in the Mississippi River Basin in the spring fuel the production of algae (primary production) in the surface waters along the continental shelf. The algae die and sink to the bottom, or something else eats the algae and the fecal matter from the something else sinks to the bottom. All that organic matter needs to decompose, and the process of decomposition (respiration) consumes oxygen. So the bottom waters on the continental shelf during the summer become very depleted in oxygen, or “hypoxic”.

Scientific research over the last few decades has shown that the increase in nitrogen flow from the Mississippi and neighbouring Atchafalaya Rivers since the 1950s has driven the development of these large seasonal periods of hypoxia. The evidence comes from basic ecological theory on nutrient limitation, lab experiments, tracking of the Mississippi River plume, long-term data analysis, sediment cores, isotopic analysis and mathematical modeling. While other nutrients like phosphorus and silica are important, nitrogen is the primary culprit.

There are many possible explanations for the increased flow of nitrogen out of the Mississippi-Atchafalaya River Basin (MARB) including fertilizer use, manure use, NOx emissions from cars and sewage. A simple nutrient budget shows nitrogen fertilizer use in the MARB has increased 20-fold since the 1950s. And today, most of that nitrogen fertilizer is applied to corn fields. Measurements and mathematical modeling of nitrogen loss from corn fields show that corn production is a primary source of nitrogen to the Mississippi and Atchafalaya Rivers, and hence, a primary driver of the development of what's come to be called the “Dead Zone”.

The author of the NCGA report (from the consulting firm StrathKirn Inc.) attempt to counter the mass of scientific evidence with the following largely baseless and unscientific arguments. Basically, he throws a bunch of stuff at the wall to see if anything sticks. I’ll go one by one through the report's chain of five incorrect and comically inconsistent assertions:

Assertion #1: Oxygen levels on the continental shelf are not low in comparison to other parts of the ocean.

This is misleading and irrelevant. First, the large regions of upwelling in the open ocean have low oxygen concentration due to high primary production. There’s no sense in contrasting the naturally and persistently low oxygen levels in the eastern Pacific to the intermittent, seasonal hypoxia on the continental shelf of the Gulf of Mexico. Second, even if there were some sense in this comparison, the data resolution of these maps is far too poor to capture a hypoxia area, which, while among the largest in the world, is still at its largest on the order of 20,000 km2 [here’s a test – can you clearly delineate New Jersey on that map?]. The global map of marine nitrogen concentrations is even more ridiculous. The data is far too coarse to capture the plume of the Mississippi River.

Assertion #2: Hypoxia doesn’t affect the fishery (not there is any hypoxia).

The report shows no change in fish catch over the years. As Steve Carpenter of the University of Wisconsin mentioned in an e-mail, the problem is the report analyses data on fish landings, not fishing effort. The boats may come back with the same weight in fish – but it takes more time and money to get those fish.

Assertion #3: Nitrogen from the Mississippi and Atchafalaya doesn’t cause the hypoxia (not that the hypoxia affects the fishery, or that there is any hypoxia in the first place).

This argument is advanced through a series of graphs relating annual nitrogen export, annual river flow and the annual extent of the hypoxic zone. There are a number of problems here. The nitrogen and flow data are shown only since 1985, despite data existing back to the 1950s. If the graph went back thirty years, you’d see the 2-3fold increase in nitrogen export occurred between the 1950s and the 1980s. Instead, the author reports no evidence of a trend in nitrogen of hypoxia since 1993. That’s not the issue – the issue is the hypoxic zone began growing large in the 1980s because fertilizer use increased between the 1950s and the 1980s, and further increases in corn planting, say for ethanol production, may further increase the average annual extent of hypoxia.

The other glaring problem with this argument is that the report uses no statistics whatsoever. For example, after a chart of nitrogen export and hypoxia extent since 1985 is this unsupported passage:

Again, there appears to be an association between water flow and the amount of nitrite (NO2) plus nitrate (NO3), but these do not relate well to the size of the hypoxic zone (except that they are all low in the year 2000). Thus, many of the statements about the relationship between water flow, nitrogen, and the size of the hypoxic zone are inaccurate.

Some actual statistical analysis, or frankly, just eyeballing the graph, would suggest that there is a significant relationship between the annual nitrogen export from the MARB and the annual extent of the hypoxic zone. It is not a perfect one-to-one relationship between nitrogen and the extent of hypoxia because of how the weather effects mixing of oxygen in the Gulf, the load of other nutrients and a myriad of other mitigating factors. If the author had done any research, they’d find proper statistical analysis and explanations in dozens of published papers, including this one of from my own work, a 2007 paper in Limnology and Oceanography:

Between 1985 and 2004, there is a significant relationship (r2 > 0.61) between midsummer hypoxia area and the May + June nitrate flux (Fig. 1). The strength of this relationship is limited by a number of other variables, including the advection of sub-pycnoclinal waters on the continental shelf, summer tropical storms that increase vertical mixing, recycling of N sequestered in shelf sediments during previous years, and the input of other nutrients such as phosphorus (Rabalais et al. 2002; Scavia et al. 2003; Wawrik et al. 2004).


Assertion #4: Not very much nitrogen is applied to corn (not that nitrogen causes hypoxia, or that hypoxia affects the fishery, or that there is any hypoxia in the first place).

The report displays a graph illustrating that non-crop uses of nitrogen fertilizer, like fertilizer used on lawns, is equal to or greater than the use of nitrogen fertilizer on corn. The problem, or I should say, the most glaring problem? It is national data. Over 90% of the corn grown in the US, and over 90% of the nitrogen fertilizer applied to corn in the US, is grown in the MARB. A 1999 EPA report estimated that non-agricultural fertilizer use is only 5% of total U.S fertilizer use - and that percentage of total fertilizer use in the major producing states of the Corn Belt.

Assertion #5: No nitrogen runs off of corn fields (not that much nitrogen is applied to corn, or that nitrogen causes hypoxia, or that hypoxia affects the fishery, or that there is any hypoxia in the first place).

The report proudly claims that the same amount of nitrogen is now removed during the corn harvest (i.e. in the grain) than is applied as fertilizer, so there can’t be any extra nitrogen left over to run off into the river. Fertilizer use efficiency has indeed increased over the years thanks to genetic technology and improved management. In other word, farmers are getting higher yields with the same amount of nitrogen fertilizer. That is positive news.

But the calculation in the paper is full of flaws. To name just one: the contention that fertilizer inputs = crop outputs = no nitrogen runoff only makes sense if fertilizer were the one and only source of nitrogen to the crops. For one, there is the mineralization of nitrogen in the soil – plant matter on the ground is naturally broken down by microbes, a process that released nitrogen from the plant matter to replenish the soil. This is a fundamental part of soil chemistry. The whole reason the Midwest is good land for growing corn is the high natural mineralization rates!

Final take-home message of the report: The US has a lot of golfers.

The report concludes that all other analyses are ignoring all the fertilizer applied to lawns and present maps and data to support this conclusion. The calculations are extremely suspect. First, the author assumes that the fraction of land devoted to lawns is greater in the MARB than in the rest of the country. Analysing the lawn data, eyeballing the national map, or simply reflecting about the fact that 4/5ths of the US population live outside the MARB, shows that this is a ridiculous assumption. Second, the report assumes that all the fertilizer not applied to corn, wheat, soybeans or cotton – which amounts to about 25% of annual fertilizer sales - is applied to lawns. This ignores all other crops grown in the United States, as well as all the fertilizer applied to rangelands and forests.

The report goes on to argue:

Since most lawns are cut and mulched there is relatively little removal of N, unlike the grain in corn. Consequently, a major portion of the N applied to lawns may be available for leaching… the net N available for leaching per acre is almost infinitely higher for lawns than from corn.

Not only does this argument incorrectly imply that no plant residue whatsoever is ever left behind after harvest to replenish the soil, it ignores the fact that unlike lawns, many corn fields are artificially drained by pipes or drainage tiles, such that excess nitrogen easily leaches to the nearest stream.

All told, the NCGA report is an embarrassment.

There are some legitimate outstanding questions about the nitrogen-hypoxia problem and definitely some legitimate critiques of the media coverage. In particular, the coverage often gives the mistaken impression that corn is the only source of nitrogen, that the hypoxic zone covers a large fraction of the Gulf of Mexico, that water at all depths is hypoxia, and that hypoxia is a permanent phenomena, rather than a seasonal occurrence. The NCGA could have issued on a report on those real concerns. Instead, it issued this dishonest mess of half-truths and pseudo-science.

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Quote of the week

And then there is We the People. Attention all young Americans: your climate future is being decided right now in the cloakrooms of the Capitol, where the coal lobby holds huge sway. You want to make a difference? Then get out of Facebook and into somebody’s face. Get a million people on the Washington Mall calling for a price on carbon. That will get the Senate’s attention. Play hardball or don’t play at all.

- Thomas Friedman, July 1

All the grassroots organizers that came out for Obama during the campaign should get to work. Canadians too. Europeans as well. If those of you outside the US want to see action in our own countries [ie. Canada] and want to see meaningful international policy [ie. Europe], you need the US to pass this the Waxman-Markey bill. Yes, it is horribly flawed. It is also the only hope right now for meaningful US political action on climate change.

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