Archive for October, 2015

Lessons from Tambora

Friday, October 30th, 2015

As time runs out for us to stop the planet from warming further, stratospheric aerosol-based Solar Radiation Management continues to be a possible option. No one believes that it solves the problem – at best it buys more time for us to control our emission of greenhouse gases.

Solar Radiation Management could involve a number of radiation reflection technologies, but sulfate injection into the stratosphere most discussed (geoengineering.weebly.com)

Solar Radiation Management could involve a number of radiation reflection technology, but sulfate injection into the stratosphere most discussed (geoengineering.weebly.com)

Most scenarios involve injecting sulfates into the stratosphere, but alumina and even diamond dust have been proposed. The idea of course is to shield the Earth’s surface from incoming solar radiation. The most conservative approach would involve injections that would build slowly, complementing CO2 emission mitigation and perhaps CO2 capture, and would be reduced and terminated as mitigation efforts grow. One author calls this the ‘less sub-optimum’ scenario.

It probably is.

We do, however, have plenty of relevant if uncontrolled experiments to think about before jumping for the SRM solution: the eruption of volcanoes. A major eruption, particularly a tropical one, ejects a massive amount of sulfates into the stratosphere 20-40 km above the Earth’s surface. Detected in the ice-cores of Greenland and Antarctica, each of the 16 largest eruptions over the past 2500 years was followed by a decade of colder temperatures, reflected by slower growth in tree ring samples.

The largest eruptions of the past 2500 years. The eruption of Tambora in 1815 (in red on lower right) was the 6th largest (nature.com).

The largest eruptions of the past 2500 years. The eruption of Tambora in 1815 (in red on lower right) was the 6th largest (nature.com).

So the connection is very clear: reduce the incoming solar radiation with reflective stratospheric particulates, and the planet cools a little.

Sounds too good?

For most major volcanic eruptions we have only the vaguest of information about subsequent biological and sociological effects. Fortunately, we now have a detailed account of the aftermath of one of the largest of these eruptions. Tambora – The Eruption that Changed the World by Gillen D’Arcy Wood, recently published, tells the astonishing tale.

Tambora's explosive eruption in 1815 caused extreme local damage in Indonesia while ejecting massive amounts of sulfates into the stratosphere (wikipedia.com)

Tambora’s explosive eruption in 1815 caused extreme local damage in Indonesia while ejecting massive amounts of sulfates into the stratosphere (wikipedia.com)

Tambora was a 13,000 ft (4000 m) peak on Sumbawa Island of the Indonesian archiplelago until, in 1815, it blew much of its top half 30-40 km up into the stratosphere. Though no one at the time made the connection, the sulfate ash cloud spread quickly around the planet with cascading cataclysmic impacts over the next three years. Wood has explored the events and connected them convincingly.

The volume of ejecta from the eruption of Tambora was immensely greater than any of the other more famous volcanic eruptions (abnextphase.com)

The volume of ejecta from the eruption of Tambora was immensely greater than any of the other more famous volcanic eruptions (abnextphase.com)

In Europe, the US Atlantic States, Yunnan Province in China, Bangali India, Indonesia – crops failed for two years, harvests were lost to frost, drought and floods, while starvation and famine killed huge numbers of people, forced populations into riots and survivors into emigrants, tearing apart the social fabric of communities and families. Cholera raged in Bengal, Typhus spread though Ireland. Meanwhile, Shelley and Byron wrote sensitive apocalyptic poems based on what they saw in Switzerland while Turner painted his famous sunsets in England.

Records of Tambora’s impact on Africa, South America and Australia don’t seem to exist. But though so much of Europe and eastern North America was devastated, Russia and the US states and territories further west were unaffected: there farms flourished and farmers sold their grains at high prices to starving Europeans and Atlantic Americans. Destitute eastern Americans migrated west to the rich grain-growing land around the Mississippi.

Europe in 1816 and 1817 experienced cold, crop failures and  starvation. Russia did not, and sold grain to Europe at high prices (scied.ucar.edu)

Europe in 1816 and 1817 experienced cold, crop failures and starvation. Russia did not, and sold grain to Europe at high prices (scied.ucar.edu)

And then in 1818 the skies finally cleared, bumper harvests returned, and the misery receded. Some repercussions persisted – shifts in attitudes about colonialism in India and optimism in the US, a shift to opium poppy growing in Yunnan, and cholera drifted on around the planet. As well, the US western farmers lost their market and their farms, bringing on the US depression of 1819-22.

During the three year impact of Tambora’s eruption, global mean temperatures appear to have abruptly dropped only about 1 degree Centigrade, yet many places around the planet experienced the crop failure, famine, epidemic disease, and catastrophic social disruption. Wood’s account is both gripping and very worrisome.

So we are well warned. If we do too little about the rate of current climate change, the scenarios are bleak. If we intentionally embark on Solar Radiation Management, we will without doubt provoke a cascade of unintended effects that could be just as bleak.

There is no quick fix. Our only option remains what it has always been. The importance of the upcoming Paris Conference on Climate Change grows ever greater.

Global Bleaching of Corals. Again

Thursday, October 22nd, 2015

When water temperatures rise a degree or two, corals expel their symbiotic algae – zooxanthellae – and turn white. It happens frequently on a local scale, and the affected corals usually recover when the sea cools again.

When bleaching occurs, symbiotic algae are lost, the coral (this one is a brain coral) will die and crumble unless sea temperature drops and the zooxanthellae can recolonize the coral (compareinnovationtoronto.com)

When bleaching occurs, symbiotic algae are lost, the coral (this one is a brain coral) will die and crumble unless sea temperature drops and the zooxanthellae can recolonize the coral (compareinnovationtoronto.com)

Summer sea surface temperature just one degree warmer than usual, lasting for 4-6 weeks, is enough to start the bleaching – corals clearly live, and thrive, at temperatures close to those that bleach and kill them.

When much of the sea surface around the tropics remains warmer for a prolonged period, the bleaching spreads, corals die and reefs are heavily damaged. The last really major global bleaching event occurred in 1997-98, while a less extensive one occurred in 2010.

A now iconic picture of part of a reef in Samoa taken before and after the onset of the current global bleaching event (sciencealert.com)

A now iconic picture of part of a reef in Samoa taken before and after the onset of the current global bleaching event (sciencealert.com)

And now, starting before the current El Nino emerged and compounded by the huge, warm ‘Pacific Blob’, we are well into another global bleaching event. With the current El Nino now growing into something fierce, this bleaching event could last a couple of years, long enough to kill and crumble a lot of the corals.

NOAA has produced a remarkable, satellite-based interactive global coral watch website, where you can observe the conditions change over the next few months. It’s scary, but it’s fascinating.

Coral bleaching isn’t new, but the 1997-1998 event was the greatest in hundreds, perhaps thousands of years. Now we have another of the same or greater magnitude. Again most reefs will be damaged. Last time, global loss was about 10%. This time it will be as much or more. It is a devastating prognosis.

NOAA October 2015 prediction of 60% probability of coral bleaching over the next four months (coralwatch.noaa.gov)

NOAA October 2015 prediction of 60% probability of coral bleaching over the next four months (coralwatch.noaa.gov)

Some protective efforts that would reduce other sources of stress on the reefs are possible, for instance reducing both pollution and overfishing, especially of algal grazers. Closing reefs to all fishing would be best. Unlikely perhaps, but not impossible.

We can as well look for other lines of hope. For instance, corals vary latitudinally in their tolerance of thermal stress, and there appears to be a genetic basis to this variation. In tanks at the National Sea Simulator at Melbourne, biologists are growing different strains of coral species under conditions of warmer temperatures and higher acidity, hoping to select for those more tolerant of the coming conditions, planning then to seed them back on the reefs. Of course this is worth doing.

Sea surface temperatures have been higher than normal for the past year, not related to the Pacific Blob or to El Nino. Now they will remain high or higher as the El Nino heat spreads and lingers (dnlr.hawaii.gov)

Sea surface temperatures have been higher than normal for the past year, not related to the Pacific Blob or to El Nino. Now they will remain high or higher as the El Nino heat spreads and lingers (dnlr.hawaii.gov)

Yet the Great Barrier Reef covers 135,000 square miles and since 1985 half of its coral cover has been lost; little remains of Caribbean coral reefs; the coral reefs around Hawaii and elsewhere in the Pacific have never been under such stress. The future of coral reefs is really bleaker than ever.

For now, the Pacific Blob will eventually dissipate. The new El Nino will slowly play itself out. Sea temperatures will drop back at least in the direction of normal. Parts of coral reefs not too damaged should slowly recover once again.

But we are warned: sea temperatures rising because of climate change rather than El Ninos will not revert to past ‘normal’ temperatures. At best their rise can be slowed by enlightened global agreement to curtail the emission of greenhouse gases,

The current global coral bleaching event is growing as we head into December’s UN Conference on Climate Change in Paris – a conference that is perilously close to being our last chance to take significant global action. Threatened, damaged, bleaching, crumbling coral reefs are not a bad metaphor for the state of our planet’s climate to remind global politicians that no longer can we afford politics as usual.

 The very odd logo for the UN Conference on Climate Change, COP 21, Nov 30-Dec11: the whole world will be watching (unfccc.int)

The very odd logo for the UN conference on Climate Change, COP 21, Nov 30-Dec11: the whole world will be watching (unfccc.int)

They – we – really have to do it this time.