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Gradual Climate Changes Could Cause Sudden Impacts

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Abrupt shifts in the climate have already begun, with more possible by the end of this century according to a report released Tuesday by the National Research Council. At the same time, even gradual changes to the climate could lead to more unforeseen, sudden impacts. The report recommends creating an early warning system, instead of simply reacting to the changes.

Greenhouse gas emissions from human activities have already altered the climate. Most changes have been gradual, but the possibility of abrupt shifts concerns the scientific community. Anthony Barnosky, a paleoecologist at University of California, Berkeley, likened gradual changes to being able to see the road while driving. With unexpected changes, the “road drops out from under you,” he said at a press conference.

A map showing temperature changes in 2100 compared to the 20th century average under a very high greenhouse gas emissions scenario.
Credit: NOAA View

Tipping points from abrupt climate change became a research priority in the early 2000s. At that time, there were growing concerns that melting ice in the northern Atlantic could cause ocean circulation to come to a halt.

“Since then, knowledge has gotten better,” Richard Alley, a geoscientist at Penn State and one of the report’s authors, said in an interview. “Now we are less worried about an Atlantic shutdown.”

The new report highlights shifts that are of growing concern. The precipitous decline of summer Arctic sea ice since 1979, but particularly over the past decade, is one of the most notable sudden changes already occurring. That trend is likely to continue and have a cascade effect on ecosystems in the region as well as impacting shipping, oil and natural gas exploration, and national security.

While changes in the Arctic might be most visible, it’s changes in the globe’s lower latitudes and oceans that are of equal or greater concern, Alley said. Those areas are where the majority of people and animals live and most of the world’s food is produced.

The current rate of climate change is one most likely not seen in 65 million years. The rate of warming is likely to increase in the coming century, and that means some species, particularly those in mountainous regions, might not be able to adapt fast enough or they’ll simply run out of room to migrate.

The top map shows velocity of climate change estimates based on the new Science study. The bottom map shows velocity of climate change based on previous estimates. Note the two maps use different scales.
Credit: Diffenbaugh and Field, 2013

Beyond changes, Alley said the report also focuses on impacts including, “more strongly emphasizing that even gradual climate change can have abrupt impacts on people and ecosystems.”

Agriculture was one area in particular where Alley thought gradual shifts in temperatures could pose problems for crops and the farmers that grow them.

“By end of the century, average summers are supposed to be hotter than the hottest we’re already seeing,” he said. “Our food is already heat stressed. If we move to unprecedented levels (of warmth), what does that do for eating?”

Research indicates that by 2050, global corn yields could fall 15 percent if greenhouse gas emissions continue on their current trajectory. Most U.S farmers have the means to adapt to or offset such decreases by planting alternative crops or investing in drought-resistant strains of corn or increased irrigation.

But for farmers in developing countries, the options are much more limited. Yields of wheat, other cereal crops, and rice are also likely to decrease in areas where they’re most needed, particularly in Africa and India, compounding the problem.

Sea level rise is also a gradual shift that could have a big consequences for coastal communities. In the U.S., coastal communities contributed $6.6 trillion to the national GDP in 2011 and population density along the coast is four times greater than inland. Globally, sea level has risen about 9 inches since 1880, but the rate of change varies based on local conditions.

Slow and steady changes in the ocean’s height can cause major damage to coastal infrastructure. Alley used New York’s subway system during Superstorm Sandy as an example.

“Either the water got into it the subway or it didn’t. The difference can be billions and billions of dollars,” he said. “A pretty small sea level change can be sufficient to push you over that threshold and make a really big difference.”

Damage on Staten Island in the immediate aftermath of Sandy. Despite scenes like this and calls for a new conversation around climate, the storm has had no lasting impact on the national discourse.
Credit: Somayya Ali/NASA GISS

Both worries about sudden climate shifts and the potential of gradual ones to create jarring impacts led the authors to recommend developing an early warning system for unanticipated climate shifts and impacts.

“It would include a lot of elements that we already use to keep track of the climate,” Alley said.

Satellites, weather stations, and greenhouse gas monitoring efforts would all likely be key components. Alley said that some of them, notably satellites, have been threatened by funding cuts in the U.S., which could hamper the development of a warning system.

Understanding little-known elements of the climate system is another important part of assessing threats. The West Antarctic Ice Sheet contains enough ice to raise sea levels 10-13 feet. Sediment records where the ice sheet meets the ocean indicate that it’s capable of rapidly flowing into the ocean and melting, but what it takes to push it over the edge is unclear. Reducing that level of uncertainty could provide coastal cities critical information on how to adapt.

Understanding who and what are most vulnerable to these threats is key, too. Some of those efforts are underway, particularly at the local level. Alley cited New York’s work in the wake of Superstorm Sandy to identify vulnerable infrastructure and populations across the city as well as U.S. Forest Service efforts to use bark beetle outbreaks to predict where large wildfires would occur as two key examples.

Putting these pieces together will ultimately require a concerted effort that brings together physical and social scientists along with decision makers. The Famine Early Warning Systems Network, which was created in the wake of the East Africa famine in the mid-1980s, and a drought warning system in the U.S. both provide lessons of how an abrupt climate change early warning system could function.

By following these and other examples, the authors envision a tool that would give decision makers a timeframe to take proactive measures for what they call “inevitable surprises” rather than reacting to them.
 

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Hurricane Sandy Hasn't Shifted Climate Narrative
Australia's Bushfires and the Role of Climate Change
Floods May Cost Coastal Cities $60 Billion a Year by 2050

Comments

By wavettore (USA)
on December 4th, 2013

The shifting of the Earth’s poles has happened a few times in the past and more than likely it will happen again. We have already found buried under seas and deserts entire cities that could not have existed in their current environment. What determines the spinning direction of our Planet is the weight of the mass on Earth and its location on our Planet that generate one magnetic field. The shifting of its mass causes a consequential change in the Earth’s magnetic field. Whichever direction the Earth will turn it will always create two poles that will freeze for lack of motion (hence lack of heat). The current global warming in the atmosphere is already diminishing the weight of the icebergs on both poles. That could cause a redistribution of the weight on the surface of our Planet and cause It to spin on a different axis. Sudden jolts and abrupt turns could disorient places and environments on our Planet and could result in a new beginning for the life that will survive.

http://www.wavevolution.org/en/freethinking.html

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By James Greyson (Lewes/East Sussex/BN8)
on December 4th, 2013

I don’t understand why abrupt climate change requiring radical abrupt societal response keeps getting reported as “gradual climate change” requiring “early warning systems”. Science and media singing lullabies when we need a wake up call? http://blindspot.org.uk/projects/#crc

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By James Thomas Thompson (Ypsalanti Mi 48197)
on December 5th, 2013

Fossil fuels should be taxed as do cigarettes for preserving our planet for future generations and used exclusively for research and development of lowering the cost of green energy.
We need to understand that the oceans are vaporizing and depositing the water on our land masses at an alarming rate.
It seems that it is always raining buckets. Clouds are so water laden due to the sun vaporizing the tops of the clouds thereby cooling and condensing the water vapor into buckets of rain.

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By Eric Peterson (Front Royal, VA 22630)
on December 5th, 2013

“The current rate of climate change is one most likely not seen in 65 million years.”

Remove the word “million” and that claim would be pretty accurate.  The current rate of global average temperature increase (less than 0.1C per decade) is less than the rate from about 1920 to 1940.

““Either the water got into it the subway or it didn’t. The difference can be billions and billions of dollars,” he said. “A pretty small sea level change can be sufficient to push you over that threshold and make a really big difference.””

It’s obvious that Richard Alley is a scientist, not an engineer.  A few inches on top of a surge makes little difference.  A few feet (e.g. when the surge hits at high tide instead of low tide) makes a difference.  The engineering solution to surges is to stop the bulk of the water with offshore barriers.

In short, having read through most of this report, I found it to be full of alarmist innuendo rather than neutral facts.  For example they talk about potential acceleration of the Brewer-Dobson cycle with global warming as if it were a bad thing.  But it would be good for polar ozone.  Another example is their misuse of a reference on ocean hypoxia.  It’s true that warmer oceans hold less oxygen but that’s not what the reference is about and actually says oxygen levels could increase with global warming,

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By Eric Peterson (Front Royal, VA 22630)
on December 5th, 2013

“We need to understand that the oceans are vaporizing and depositing the water on our land masses at an alarming rate.”

There is little empirical evidence for intensification of the water cycle and certainly it is not alarming compared to natural variation.

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By James Greyson (Lewes/East Sussex/BN8)
on December 6th, 2013

Thanks Brian for your comment on twitter, “Not sure I agree with your take, though. Concern for sudden impacts very much a part of that story.”

I should explain a bit. The system we’re talking about is complex but the options can hopefully be seen with a simple 3 step linear mental model. Our actions (1) determine climate destabilising (2) which determines impacts (3). So impacts are downstream; they can tell us something about the climate problem and the necessary response. However to say that impacts are sudden doesn’t tell us about the problem or the response. Even with no climate destabilising the impacts of weather, eg storms, are usually sudden. To say we need early warnings doesn’t tell us about the problem or the response. Even with no climate instability it’s still handy to have warning of impacts from weather.

What is useful in this story is the potential for non-gradual climate instability, ie a climate cliff edge. Data gathering to guess at the contours of the cliff edge is futile and delusional. Adaptation strategy based on continuing to run toward the cliff edge is futile and delusional. What would be useful is for science and media to connect the scale of impacts to the evidence of abrupt climate change to the scale and speed of action in the human response. This would at least shift the discussion to become relevant to the problem and give us a chance of turning around and running away from the climate cliff.

Maybe I’ve missed this discussion? If it’s happening I’d be delighted to learn where.

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By kermit
on December 6th, 2013

Eric, the whole twentieth century displays the warming trend pretty clearly. The temporary drop from about 1940 to 1960 is the result of a rapid increase in aerosols - precipitates in the air from industrial exhaust. Visible smog, in other words. With the killer smog in London in 1952 the Western world took immediate and dramatic steps to reduce that pollution, and it largely worked. But a side effect was that clearer air let a more natural amount of light through, and more of its energy was retained as heat because of increasing amounts of greenhouse gases. In the current Wikipedia article on global warming there is a map on the right which shows clearly that the temperature trend from about 1900 has been up, except for that 20 year period.

http://en.wikipedia.org/wiki/File:Global_Temperature_Anomaly.svg

And gradual increases in a process certainly can cause precipitous results. Set a fine china plate on two cinder blocks, supported by its edges. Carefully set a brick on it. Add bricks carefully, one by one, until something happens. Let us know if it was sudden or gradual. If the storm surge is just a little over the levees, it is too much - the entire ocean is behind that surge, not just a few high waves. Or do you think the flooding of the subway was alarmist propaganda?

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By Eric Peterson (Front Royal, VA 22630)
on December 8th, 2013

“The temporary drop from about 1940 to 1960 is the result of a rapid increase in aerosols - precipitates in the air from industrial exhaust.”

Kermit, there is some evidence for anthropogenic sulfate aerosol deposition in ice cores.  Compare fig 3 to fig 4 here: http://climate.envsci.rutgers.edu/pdf/RobockFree95JD00825.pdf But those manmade aerosols did not “rapidly rise”, were mainly northern hemisphere, and were exceeded by natural variation (volcanic and biogenic aerosols).

Regarding surges and surge protection there is a clear engineering answer which is that overtopping of levees is common and expected and easily handled.  A few inches are not an issue, a few feet are.  Lunar and solar alignment can be responsible for a few feet and anthropogenic sea level rise a few inches (for now).  The flooding of some parts of the subway with a few feet of surge is obviously a consequence of poor planning and tidal enhancement.

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