Tag Archives: climate change

Climate change amplifies eutrophication

Hans Paerl and Jef Huisman have a perspective article in Science that reviews how climate change may promote blooms of cyanobacteria Blooms Like It Hot (320 (5872): 57 ):

Nutrient overenrichment of waters by urban, agricultural, and industrial development has promoted the growth of cyanobacteria as harmful algal blooms (1, 2). These blooms increase the turbidity of aquatic ecosystems, smothering aquatic plants and thereby suppressing important invertebrate and fish habitats. Die-off of blooms may deplete oxygen, killing fish. Some cyanobacteria produce toxins, which can cause serious and occasionally fatal human liver, digestive, neurological, and skin diseases (1-4). Cyanobacterial blooms thus threaten many aquatic ecosystems, including Lake Victoria in Africa, Lake Erie in North America, Lake Taihu in China, and the Baltic Sea in Europe (3-6). Climate change is a potent catalyst for the further expansion of these blooms.

Rising temperatures favor cyanobacteria in several ways. Cyanobacteria generally grow better at higher temperatures (often above 25°C) than do other phytoplankton species such as diatoms and green algae (7, 8). This gives cyanobacteria a competitive advantage at elevated temperatures (8, 9). Warming of surface waters also strengthens the vertical stratification of lakes, reducing vertical mixing. Furthermore, global warming causes lakes to stratify earlier in spring and destratify later in autumn, which lengthens optimal growth periods. Many cyanobacteria exploit these stratified conditions by forming intracellular gas vesicles, which make the cells buoyant. Buoyant cyanobacteria float upward when mixing is weak and accumulate in dense surface blooms (1, 2, 7) (see the figure). These surface blooms shade underlying nonbuoyant phytoplankton, thus suppressing their opponents through competition for light (8). Cyanobacterial blooms may even locally increase water temperatures through the intense absorption of light. The temperatures of surface blooms in the Baltic Sea and in Lake IJsselmeer, Netherlands, can be at least 1.5°C above those of ambient waters (10, 11). This positive feedback provides additional competitive dominance of buoyant cyanobacteria over nonbuoyant phytoplankton.

Global warming also affects patterns of precipitation and drought. These changes in the hydrological cycle could further enhance cyanobacterial dominance. For example, more intense precipitation will increase surface and groundwater nutrient discharge into water bodies. In the short term, freshwater discharge may prevent blooms by flushing. However, as the discharge subsides and water residence time increases as a result of drought, nutrient loads will be captured, eventually promoting blooms. This scenario takes place when elevated winter-spring rainfall and flushing events are followed by protracted periods of summer drought. This sequence of events has triggered massive algal blooms in aquatic ecosystems serving critical drinking water, fishery, and recreational needs. Attempts to control fluctuations in the discharge of rivers and lakes by means of dams and sluices may increase residence time, further aggravating cyanobacteria-related ecological and human health problems.

Global Glacier Decline

The World Glacier Monitoring Service‘s latest report shows that, based on data from 30 glaciers spread in nine mountainous regions of the world, glacier mass balance is negative (i.e. glacier melt exceeds ice formation) and the average mass balance is declining (i.e. more ice is melting each year).

Glacier Mass Loss

Figure 1a and 1b: Mean cumulative specific net balance (top) and mean annual specific net balance (bottom) from continuously measured on 30 glaciers in 9 mountain ranges for the period 1980-2004, on 29 glaciers in 9 mountain ranges for 2005, and on 27 glaciers in 8 mountain ranges for 2006. (see World Glacier Monitoring Service).

Andy Revkin comments on the report in Farewell to Ice on his weblog, and the USA’s National Snow and Ice Data Center host a collection of repeat photography of glaciers documenting their decline.

See also the previous post Arctic Sea ice at record low.

Biofuel production vs. Aquatic ecosystems

Simon Donner writes about his new paper Corn-based ethanol production compromises goal of reducing nitrogen export by the Mississippi River (Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0708300105) on his weblog maribo:

A new paper by my colleague Chris Kucharik and I looks at the new US Energy Policy, will calls for growing more corn to produce ethanol, will affect the “Dead Zone” in the Gulf of Mexico. For a quick summary, see Reuters, the CBC or AFP.

The Mississippi dumps a massive amount of nitrogen, largely in the form of the soluble ion nitrate, into the Gulf each spring. It promotes the growth of a lot of algae, which eventually sinks to the bottom and decomposes. This consumes much of the oxygen in the bottom waters, making life tough for bottom-dwelling fish and creatures like shrimp. The Dead Zone has reached over 20,000 km2 in recent years.

The primary source of all that nitrogen is fertilizer applied to corn grown in the Midwest and Central US. Reducing the Dead Zone to less than 5000 km2 in size, as is suggested in US policy, will require up to a 55% decrease in nitrogen levels in the Mississippi.

The new US Energy Policy calls for 36 billion gallons of renewable fuels by the year 2022. Of that, 15 billion can be produced from corn starch. Our study found meeting those would cause a 10-34% increase in nitrogen loading to the Gulf of Mexico.

Meeting the hypoxia reduction goal was already a difficult challenge. If the US pursues this biofuels strategy, it will be impossible to shrink the Dead Zone without radically changing the US food production system. The one option would be to dramatically reduce the non-ethanol uses of corn. Since the majority of corn grain is used as animal feed, a trade-off between using corn to fuel animals and using corn to fuel cars could emerge.

Social Implications of Arctic Melting

An article Arctic Meltdown in Foreign Affairs by Scott G. Borgerson discusses the political and economics consequences on a ice-free summer Arctic:

The shipping shortcuts of the Northern Sea Route (over Eurasia) and the Northwest Passage (over North America) would cut existing oceanic transit times by days, saving shipping companies — not to mention navies and smugglers — thousands of miles in travel. … Taking into account canal fees, fuel costs, and other variables that determine freight rates, these shortcuts could cut the cost of a single voyage by a large container ship by as much as 20 percent — from approximately $17.5 million to $14 million — saving the shipping industry billions of dollars a year. The savings would be even greater for the megaships that are unable to fit through the Panama and Suez Canals and so currently sail around the Cape of Good Hope and Cape Horn. Moreover, these Arctic routes would also allow commercial and military vessels to avoid sailing through politically unstable Middle Eastern waters and the pirate-infested South China Sea. An Iranian provocation in the Strait of Hormuz, such as the one that occurred in January, would be considered far less of a threat in an age of trans-Arctic shipping.

Arctic shipping could also dramatically affect global trade patterns. … As soon as marine insurers recalculate the risks involved in these voyages, trans-Arctic shipping will become commercially viable and begin on a large scale. In an age of just-in-time delivery, and with increasing fuel costs eating into the profits of shipping companies, reducing long-haul sailing distances by as much as 40 percent could usher in a new phase of globalization. Arctic routes would force further competition between the Panama and Suez Canals, thereby reducing current canal tolls; shipping chokepoints such as the Strait of Malacca would no longer dictate global shipping patterns; and Arctic seaways would allow for greater international economic integration. When the ice recedes enough, likely within this decade, a marine highway directly over the North Pole will materialize. Such a route, which would most likely run between Iceland and Alaska’s Dutch Harbor, would connect shipping megaports in the North Atlantic with those in the North Pacific and radiate outward to other ports in a hub-and-spoke system. A fast lane is now under development between the Arctic port of Murmansk, in Russia, and the Hudson Bay port of Churchill, in Canada, which is connected to the North American rail network.

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Climate Change May Transform Fire Regime in Tundra

arctic tundraPhilip Higuera and collaborators suggests that based on paleo-ecological analysis of past fire regimes, climate change could lead to abrupt shifts in tundra fire frequency as climate change vegetation shifts from herb to shrub dominated tundra.

In their article (Higuera PE, Brubaker LB, Anderson PM, Brown TA, Kennedy AT & Hu FS. 2008 Frequent fires in ancient shrub tundra: implications of paleorecords for Arctic environmental change. PLoS ONE DOI: 10.1371/journal.pone.0001744) the authors write:

… paleorecords from northcentral Alaska imply that ongoing shrub expansion and climate warming will result in greater burning within northern tundra ecosystems. The geographic extent of fire-regime changes could be quite large, as shrubs are expected to expand over the next century in both herb and low shrub tundra ecosystems, which comprise 67% of circumpolar Arctic tundra [10], [15] (Fig. 1). Over this same period, annual temperatures in the Arctic are projected to increase between 3–5°C over land, lengthening the growing season and likely decreasing effective moisture (in spite of increased summer precipitation) [8]. How long might it take for the current shrub expansion to trigger a significant change in fire frequencies? Within the chronological limitations of our records, past shrub expansion and fire-regime changes at each site occurred within a few centuries (Fig. 2). The duration of this shift is consistent with the estimated rate of shrub expansion within a large area of northern Alaska [0.4% yr−1 for ca 200,000 km2; 10]. Based on a simple logistic growth model and the assumption of a constant expansion rate, Tape et al. [10] hypothesize that the ongoing shrub expansion in this region started roughly 125 years ago and should reach 100% of the region in another 125 years. Thus, if fuels and low effective moisture are major limiting factors for tundra fires, we predict that fire frequencies will increase across modern tundra over the next several centuries.

Despite these uncertainties, Alaskan paleorecords provide clear precedence of shrub-dominated tundra sustaining higher fire frequencies than observed in present-day tundra. The future expansion of tundra shrubs [10], [16] coupled with decreased effective moisture [8] could thus enhance circumpolar Arctic burning and initiate feedbacks that are potentially important to the climate system. Feedbacks between increased tundra burning and climate are inherently complex [3][5], but studies of modern tundra fires suggest the possibility for both short- and long-term impacts from (1) increased summer soil temperatures and moisture levels from altered surface albedo and roughness [24], and (2) the release soil carbon through increased permafrost thaw depths and the consumption of the organic layer [24], [25]. Given the importance of land-atmosphere feedbacks in the Arctic [26][28], the precedence of a fire-prone tundra biome should motivate further research into the controls of tundra fire regimes and links between tundra burning and the climate system.

Climate driven changes in vegetation cover across the most northern land surfaces on the planet will likely result in more carbon-releasing fires, according to a study published this week in PLoS ONE. Philip Higuera, currently at Montana State University, and colleagues examined charcoal and pollen samples from Alaskan lakes, which provide a historical record of plant composition and fire frequency between 14000 and 10000 years ago. Back then, the tundra was dominated by extensive thickets of resin birch Betula glandulosa, and the warming climate is likely to see its widespread return to areas currently occupied by somewhat less flammable herbs. The mass of tangled, resin-laden twigs could turn the area into a tinderbox, with the double whammy that such fires encourage vigorous birch regrowth, making it prone to further blazes. The likely consequence is that another source of carbon dioxide will enter the scene, as vegetation and long-frozen soil go up in smoke.

via SCB’s Journal Watch Online

Two Energy Futures from Shell Oil

This week Shell oil published an article by their chief executive Jeroen van der Veer that presents two scenarios of global energy development – Scramble and Blueprints. Shell has long been a leader in scenario planning. Other Shell scenarios and previous Shell scenarios are also available online.

…the distant future looks bright, but much depends on how we get there. There are two possible routes. Let’s call the first scenario Scramble. Like an off-road rally through a mountainous desert, it promises excitement and fierce competition. However, the unintended consequence of “more haste” will often be “less speed,” and many will crash along the way.The alternative scenario can be called Blueprints, which resembles a cautious ride, with some false starts, on a road that is still under construction. Whether we arrive safely at our destination depends on the discipline of the drivers and the ingenuity of all those involved in the construction effort. Technological innovation provides the excitement.

Regardless of which route we choose, the world’s current predicament limits our room to maneuver. We are experiencing a step-change in the growth rate of energy demand due to rising population and economic development. After 2015, easily accessible supplies of oil and gas probably will no longer keep up with demand.

As a result, we will have no choice but to add other sources of energy – renewables, yes, but also more nuclear power and unconventional fossil fuels such as oil sands. Using more energy inevitably means emitting more CO2 at a time when climate change has become a critical global issue.

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Arctic sea ice: is it tipped yet?

RealClimate reports from the AGU about Arctic sea ice: is it tipped yet?

The summer of 2007 was apocalyptic for Arctic sea ice. The coverage and thickness of sea ice in the Arctic has been declining steadily over the past few decades, but this year the ice lost an area about the size of Texas, reaching its minimum on about the 16th of September. Arctic sea ice seems to me the best and more imminent example of a tipping point in the climate system. A series of talks aimed to explain the reason for the meltdown.

The disappearance of the ice was set up by warming surface waters and loss of the thicker multi-year ice in favor of thinner single-year ice. But the collapse of ice coverage this year was also something of a random event. This change was much more abrupt than the averaged results of the multiple IPCC AR4 models, but if you look at individual model runs, you can find sudden decreases in ice cover such as this. In the particular model run which looks most like 2007, the ice subsequently recovered somewhat, although never regaining the coverage before the meltback event.

So what is the implication of the meltback, the prognosis for the future? Has the tipping point tipped yet? When ice melts, it allows the surface ocean to begin absorbing sunlight, potentially locking in the ice-free condition. Instead of making his own prognosis, Overland allowed the audience to vote on it. The options were

* A The meltback is permanent
* B Ice coverage will partially recover but continue to decrease
* C The ice would recover to 1980’s levels but then continue to decline over the coming century

Options A and B had significant audience support, while only one brave soul voted for the most conservative option C. No one remarked that the “skeptic” possibility, that Arctic sea ice is not melting back at all, was not even offered or asked for. Climate scientists have moved beyond that.

For more coverage see Nature’s Great Beyond.

Stern: In Bali the rich must pay

Nicholas Stern, former chief economist of the World Bank and who led the Stern review on the economics of climate change, writes in the Guardian (Nov 30, 2007), that in Bali the rich must pay to produce a system to tackle climate change that is effective, efficient and equitable. He writes that A fair and global effort to tackle climate change needs wealthy states to take the lead in CO2 cuts:

The Bali summit on climate change, which starts next week, will seek to lay the foundations for a new global agreement on reducing the greenhouse gas emissions that cause rising temperatures and climate change. Ambitious targets for emission reduction must be at the heart of that agreement, together with effective market mechanisms that encourage emission trading between countries, rich and poor. The problem of climate change involves a fundamental failure of markets: those who damage others by emitting greenhouse gases generally do not pay. Climate change is a result of the greatest market failure the world has seen.The evidence on the seriousness of the risks from inaction is now overwhelming. We risk damage on a scale larger than the two world wars of the past century. The problem is global and the response must be collaboration on a global scale. The rich countries must lead the way in taking action. And in thinking about global action to reduce greenhouse gas emissions, we must invoke three basic criteria.

The first is effectiveness: the scale of the response must be commensurate with the challenge. This means setting a target for emission reduction that can keep the risks at acceptable levels.

The overall targets of 50% reductions in emissions by 2050 (relative to 1990) agreed at the G8 summit in Heiligendamm last June are essential if we are to have a reasonable chance of keeping temperature increases below 2C or 3C. While these targets involve strong action, they are not overambitious relative to the risk of failing to achieve them.

The second criterion is efficiency: we must keep down the costs of emission reduction, using prices or taxes wherever possible. Emission trading between countries must be a central part of the story. And helping poor countries cover their costs of emission reduction gives them an incentive to join a global deal.

Third, we should be concerned about equity. Our starting point is deeply inequitable with poor countries certain to be hit earliest and hardest by climate change. But rich countries are responsible for the bulk of past emissions: US emissions are currently more than 20 tonnes of CO2 equivalent per annum, Europe’s are 10-15 tonnes, China’s five or more tonnes, India’s around one tonne, and most of Africa much less than one.

For a 50% reduction in global emissions by 2050, the world average per capita must drop from seven tonnes to two or three. Within these global targets, even a minimal view of equity demands that the rich countries’ reductions should be at least 80% – either made directly or purchased. An 80% target for rich countries would bring equality of only the flow of current emissions – around the two to three tonnes per capita level. In fact, they will have consumed the big majority of the available space in the atmosphere.

Rich countries also need to provide funding for three more key elements of a global deal. First, there should be an international programme to combat deforestation, which contributes 15-20% of emissions. For $10bn-$15bn per year, half the deforestation could be stopped.

Second, there needs to be promotion of rapid technological advance to mitigate the effects of climate change. The development of technologies must be accelerated and methods found to promote their sharing. Carbon capture and storage for coal (CCS) is particularly urgent since coal-fired electric power is currently the dominant technology around the world, and emerging nations will be investing heavily in these technologies. For $5bn a year, it should be possible to create 30 commercial-scale coal-fired CCS stations within seven or eight years.

Finally, rich countries should honour their commitment to 0.7% of GDP in aid by 2015. This would yield increases in flows of $150bn-$200bn per year. The extra costs that developing countries face as a result of climate change are likely to be upwards of $80bn a year, and it is vital that extra resources are available. This proposed programme of action can be built if rich countries take a lead in Bali on their targets, the promotion of trading mechanisms and funding for deforestation and technology. With leadership and the right incentives, developing countries will join.

The building of the deal, and its enforcement, will come from the willing participation of countries driven by the understanding that action is vital. It will not be a wait-and-see game as in World Trade Organisation talks, where nothing is done until everything is settled.

The necessary commitments are increasingly being demonstrated by political action and elections around the world. A clear idea of where we are going as a world will make action at the individual, community and country level much easier and more coherent.

These commitments must, of course, be translated into action. There is a solution in our hands. It will not be easy to build. But the alternative is too destructive to accept. Bali is an opportunity to draw the outline of a common understanding, which will both guide action now and build towards the deal.

via Globalization and Environment

How slow change increased California’s fire risk

California firesThe Christian Science Monitor article California’s age of megafires describes how California’s fire risk has been increased by slow changes in fire suppression (but probably not in California), climate change, longer fire season, and house construction in the wildland-urban interface:

Megafires, also called “siege fires,” are the increasingly frequent blazes that burn 500,000 acres or more – 10 times the size of the average forest fire of 20 years ago. One of the current wildfires is the sixth biggest in California ever, in terms of acreage burned, according to state figures and news reports.The trend to more superhot fires, experts say, has been driven by a century-long policy of the US Forest Service to stop wildfires as quickly as possible. The unintentional consequence was to halt the natural eradication of underbrush, now the primary fuel for megafires.

Three other factors contribute to the trend, they add. First is climate change marked by a 1-degree F. rise in average yearly temperature across the West. Second is a fire season that on average is 78 days longer than in the late 1980s. Third is increased building of homes and other structures in wooded areas.

“We are increasingly building our homes … in fire-prone ecosystems,” says Dominik Kulakowski, adjunct professor of biology at Clark University Graduate School of Geography in Worcester, Mass. Doing that “in many of the forests of the Western US … is like building homes on the side of an active volcano.”

In California, where population growth has averaged more than 600,000 a year for at least a decade, housing has pushed into such areas.

“What once was open space is now residential homes providing fuel to make fires burn with greater intensity,” says Terry McHale of the California Department of Forestry firefighters union. “With so much dryness, so many communities to catch fire, so many fronts to fight, it becomes an almost incredible job.”

Arctic sea ice at record low

In 2005 on Resilience Science, Line Gordon, wrote about recent research that we may have already passed tipping points in the Arctic.

NSIDC Arctic Sea Ice News Fall 2007 is providing weekly updates on the state of Arctic sea ice, which has reached record low coverage this year (the previous record low was in 2005).

Arctic Sea Ice

The figure shows daily ice extent for 2007, 2005 and to the 1979 to 2000 average.