Tag Archives: climate change

The Statistical Probability That Climate Change Is Not Manmade Is 0.01 Percent

That climate science relies too heavily on models is one of the last arguments that climate change deniers cling to—many of them argue that proving climate change is manmade is impossible. But one researcher says he’s basically just done the opposite: he used statistics, actual observed data, and, most importantly, no computer models at all to prove that climate change has not been a natural phenomenon…. read the rest here

 

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Climate change is already changing the Australian landscape

from David Donaldson at the Guardian

Climate zones along the coast of southeastern Australia have already moved south by around 350km. Those fluctuations are also altering the way rural communities live.

tree guardian

I was in high school when crested pigeons started showing up at the farm where I grew up. Situated in a flat, pastoral corner of southwest Victoria, the pointy-haired birds first seemed out of place – a budding wildlife enthusiast, I’d previously only seen photos of them in the desert.

But thanks to the millennium drought – which became progressively worse from around the time I started primary school until my final year of high school – the crested pigeons had obviously decided southwest Victoria was now sufficiently dehydrated for them to take up residence. Though the drought ended several years ago, the pigeons are now a permanent fixture on the farm; I hear their distinctive whirring sound every time I go back to visit.

The same thing happened with galahs when my father was young. The pink and grey cockatoos flew in from the north during the 1965-68 drought and have never left. Other birds, such as the charismatic grey fantail, have changed their migratory behaviour in recent years as winters become milder and shorter, as have countless species right around the world.

It’s not just the wildlife that’s changing. The hotter, drier climate gradually imposing itself on southeastern Australia is forcing changes to agriculture. In southwest Victoria, this means it’s becoming harder to produce the beef and wool my father grew when I was a child. Cereal cropping, which uses less water and creates fewer jobs, is becoming more popular.

A Crested Pigeon.
A Crested Pigeon. Photograph: Ed Dunens/Flickr

Old European trees in gardens and town centres are dying in the long, waterless summers. Aquifers are becoming harder to access as runoff remains low, while decreasing autumn precipitation is leading to a shorter growing season. Frosts are becoming less common, though clear skies, which allow heat to escape at night-time, mean minimum temperatures are not increasing at the same rate as maximums.

The changes are also altering the way rural communities live. The drought in particular had a huge and traumatic effect. Livestock previously had to be shot when feed and water ran out. Many workers ended up leaving farming because it was just too hard. Tragically, the suicide rate among farmers spiked during the final years as entire livelihoods were reduced to dust. Though drought is a recurrent theme of the Australian landscape, this one was especially long and harsh – and the research suggests such phenomena will only become more common.

As the IPCC’s fifth assessment report has reiterated, climate change is not merely a beast of the future – it’s been happening for a while. Victoria’s average annual mean temperature has increased by almost 0.9°C over the past century, around the same as the rest of Australia. Although rainfall is more variable, droughts are becoming longer and drier. Record high temperatures are regularly broken, while record lows are becoming harder to find.

Climate zones along the coast of southeastern Australia have already moved south by around 350km. Those on the northeast coast have shifted around 200km. Fish species are travelling further south than before. Long-spined sea urchins, previously found only as far south as southern NSW, have been caught in eastern Tasmania. Other organisms have specific, geographically-bound ranges that do not allow them to move, and will find it difficult to adapt to warmer seas.

Terrestrial animals will increasingly face the same problem. Our national parks are poorly connected in large areas of Australia, meaning many creatures will be unable to migrate as temperatures increase. Some animals escaping monsoonal northern Australia will find it difficult to survive in drier inland areas. Alpine animals, such as the Leadbeater’s Possum, will be especially challenged as thin snowfall and bigger bushfires cause their habitat to disappear.

But while the outlook is concerning for agricultural production and downright terrible for our natural habitat, there are a few glimmers of hope. It’s reassuring that, despite the acrimony surrounding climate politics at a national level, there are plenty of community groups and governmental bodies conducting important research into how we deal with a hotter, drier Australia. While politicians and vested interests have muddied the waters of public opinion for strong action to stop climate change, pragmatism based on evidence is leading progress in adaptation and mitigation.

Though it may be politically conservative, southwest Victoria is no exception. In 2013 for example, Moyne shire released an extensive coastal hazard assessment report for popular holiday town Port Fairy, finding that several hundred buildings would be at risk of inundation by seawater as ocean levels rise.

Individual farmers, landcare groups and catchment management authorities are working on a range of projects to increase biodiversity and improve agricultural processes. Nationally, the CSIRO is breeding new types of drought-tolerant wheat that will hopefully prevent a decline in productivity as the landscape becomes drier.

We’re already seeing the effects climate change is having on the natural world. Even if governments start making a serious effort to combat climate change today, we won’t be starting from zero – the clock started long ago, but we’re still crouched at the starting block.

Sooner or later, we’ll all be touched by climate change in some way, as indeed many already have. Hopefully we’ll be prepared for it.

Original story here

 

 

 

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another clean up

Just sorting through a few things and for the sake of posterity am posting these pictures here.  They are the latest in my take on what’s going on in Australian politics. As usual, feel free to use these if you like.

First, Joe Hockey announced that everyone is going to have to engage in some heavy lifting to fix the budget….which if it’s in any trouble it’s due completely to Sloppy Joe Hockey borrowing the most money in the history of Australia.

heavy lifting

The next few are self-explanatory…

tony denialracist trashDowntonabbott

Abbott, in his usual thoughtless way announced another brainfart without considering the ramifications, as he showed just how out of touch he is by stating that social media is “digital graffiti”. Interesting….like this?

abbottsux

Then we have Mr Sinodinos, the soon to be former Assistant Treasurer, who has fronted an inquiry into all sorts of shady dealings.

corrupt

Then there is this…

TPP ISDS

and this…

reza barati

Finally, I received, along with a lot of other people on Facebook, one of these simple maths tests where you either like or make a comment depending on your answer. I was disgusted with the amount of likes compared to comments but even worse were some of the comments having an answer that was even more wrong, prompting me to offer a third alternative….

improved FB maths test

I mean, seriously? This is pretty basic maths. If people can’t even get this very simple arithmetic correct, what hope of understanding the complexity of anthropogenic climate change?

Anyway, that’s part of my week. Another big part was going to be a discussion on the similarities between the far loony right and the far loony left after witnessing and engaging in a discussion on another blog about veganism, but that’s for another day….maybe.

 

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IPCC WG2 Climate Change 2014: Impacts, Adaptation, and Vulnerability

Instead of relying on leaked drafts of this report, you can now download the final version. Before you do though, please have a read of Graham Readfearn’s take, but before you do even that, please consider this story from the New York Times about the awful mudslide in Oso, Washington. To me, it is almost an analogy for the entire human race and our human caused climate change.

A Mudslide, Foretold

Timothy Egan

DON’T tell me, please, that nobody saw one of the deadliest landslides in American history coming. Say a prayer or send a donation for a community buried under a mountain of mud along a great river in Washington State, the Stillaguamish. Praise the emergency workers still trying to find a pulse of life in a disaster that left 25 people dead and 90 missing.

But enough with the denial, the willful ignorance of cause and effect, the shock that one of the prettiest valleys on the planet could turn in a flash from quiet respite in the foothills of the North Cascades to a gravelly graveyard.

“This was a completely unforeseen slide,” said John Pennington, the emergency manager of Snohomish County. “It was considered very safe.” He said this on Monday, two days after the equivalent of three million dump truck loads of wet earth heaved down on the river near the tiny town of Oso. Unforeseen — except for 60 years’ worth of warnings, most notably a report in 1999 that outlined “the potential for a large catastrophic failure” on the very hillside that just suffered a large catastrophic failure.

It is human nature, if not the American way, to look potential disaster in the face and prefer to see a bright and shining lie. The “taming” of this continent, in five centuries and change, required a mighty mustering of cognitive dissonance. As a result, most of us live with the danger of wildfire, earthquake, tornado, flooding, drought, hurricane or yet-to-be-defined and climate-change-influenced superstorm. A legacy of settlement is the delusion that large-scale manipulation of the natural world can be done without consequence.

What happened when the earth moved on a quiet Saturday morning in the Stillaguamish Valley was foretold, in some ways, by the relationship that people have with that sylvan slice of the Pacific Northwest.

Almost 25 years ago, I went into one of the headwater streams of the Stillaguamish with Pat Stevenson, a biologist with the American Indian tribe that bears the same name as the river and claims an ancient link to that land. The rain was Noah-level that day — just as it’s been for most of this March.

We drove upriver, winding along the drainage of Deer Creek, one of the main tributaries of the Stillaguamish. We couldn’t see Whitehorse Mountain, the dreamy peak that towers over the valley, that day. We could barely see beyond our windshield wipers. At last, we arrived at an open wound near road’s end. I’d never witnessed anything like it: an active slide, sloughing mud and clay down into the formerly pristine creek. We watched huge sections of land peel and puddle — an ugly and terrifying new landscape under creation before our eyes.

Stevenson pointed uphill, to bare, saturated earth that was melting, like candle wax, into the main mudslide. Not long ago, this had been a thick forest of old growth timber. But after it was excessively logged, every standing tree removed, there was nothing to hold the land in place during heavy rains. A federal survey determined that nearly 50 percent of the entire basin above Deer Creek had been logged over a 30-year period. It didn’t take a degree in forestry to see how one event led to the other.

The Stilly, as locals call the river, is well known to those who chase fish with a fly rod, and to native people who have been living off its bounty for centuries. Zane Grey, the Western novelist, called it the finest fishing river in the world for steelhead, the big seagoing trout that can grow to 40 pounds. What Stevenson showed me that day in a November storm was how one human activity, logging, was destroying the source of joy and sustenance for others. When the crack and groan of an entire hillside in collapse happened a week ago Saturday, I thought instantly of Stevenson and that gloomy day at Deer Creek.

And, sure enough, logging above the area of the current landslide appears to have gone beyond the legal limits, into the area that slid, according to a report in The Seattle Times.

Yes, but who wants to listen to warnings by pesky scientists, to pay heed to predictions by environmental nags, or allow an intrusive government to limit private property rights? That’s how these issues get cast. And that’s why reports like the ones done on the Stillaguamish get shelved. The people living near Oso say nobody ever informed them of the past predictions.

Just upriver from the buried community along the Stillaguamish is Darrington, a town with a proud logging tradition. The folks who live there are self-described Tarheels, transplanted from Southern Appalachia several generations ago after their own timber mills went bust. They hold a terrific bluegrass festival every year, and they show up in force at public hearings where government and environmentalists are denounced with venom. It’s not their fault that the earth moved, certainly. But they should insist that their public officials tell them the plain truth when the science is bad news.

An Act of God is a legal term to describe an event outside of human control. No one can be held responsible. Exactly 50 years ago Thursday, in Alaska, the second largest earthquake in recorded history, magnitude 9.2, remade the Last Frontier State. What had been gravel beaches rose to become 30-foot cliffs. What had been forests at sea level were submerged, leaving only the ghostly silver tips that you can still see. In Anchorage, 42,000 people were left homeless.

That quake was an Act of God. Even so, cities along the West Coast have adopted strict seismic standards to lessen the human misery, should another earthquake of that size strike.

The Dust Bowl, arguably the greatest environmental disaster in American history, was not an Act of God. A drought, even a prolonged one, was no stranger to the High Plains — same as heavy rain is to the west side of the Cascade Mountains. But those regions have been considerably altered by human hands. In both cases, you love the land, but you should never forget that it can turn on you.

Now, I’m an atheist, so the whole “Act of God” thing doesn’t even register in my thoughts as everything has a cause and most things arise from chance. Anthropogenic climate change, like the American Dust Bowl, is not occurring due to chance. It is most definitely of our making. The predictions and warnings have been coming from the scientific community for much longer than the 25 years or so of IPCC reports and yet, still our emissions continue to grow and at some point, like the millions of tons of mud in Oso, Washington, climate change will come crashing down on us.

Graham Readfearn’s take is here

The IPCC report is here.

The original NYT article is here.

 

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The hellish monotony of 25 years of IPCC climate change warnings

This is the title of the latest article from Graham Readfearn at the Guardian. For me, I think an equally acceptable one would be…

25 years with our heads in the sand. Not even ostriches are stupid enough to do that.

Anyway, Graham writes…

The latest blockbuster United Nations report on the impacts of climate change makes dire reading, just as the first one did almost a quarter of a century ago.

Entire island nations “rendered uninhabitable”, millions of people to be displaced by floods and rising seas, uncertainties over global food supplies and severe impacts on human health across the world.

The news from the United Nations on the likely impacts of climate change is dire, especially for the poorest people on the planet.

There will likely be more floods, more droughts and more intense heatwaves, says the UN’s Intergovernmental Panel on Climate Change.

As human emissions of greenhouse gases continue to rise, natural ecosystems come under extreme stress with “significant” knock-on effects for societies….

Read the full article here.

 

 

 

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Tony Abbott’s “Direct (in)Action” plan flawed.

Everyone knows it, even the coalition themselves. The vast majority of them are climate change deniers and their plan will actually put money in the pockets of polluters and allow them to increase emissions. Now, a Senate committee has examined the plan and given it a huge tick of disapproval.

from the Guradian

‘Flawed’ Direct Action climate plan should go, says Senate committee

Increased cuts in emissions and floating carbon price recommended to replace Coalition scheme

cooling towers

The federal government’s climate change plan is “fundamentally flawed” and should be ditched in favour of a floating price on carbon, a Senate committee report has found.

The committee report recommended the government “immediately adopt” the emissions reduction targets put forward by the independent Climate Change Authority, which the Coalition has vowed to disband.

This would deepen the cut in emissions by 2020 – from the present target of 5% – to 15% below levels in 2000. The cut would become 19% if Australia’s Kyoto Protocol commitments were factored in.

The committee also recommended the clean energy package introduced by the previous Labor government should not be repealed, including the retention of the Clean Energy Finance Corporation, which the government again moved to abolish on Thursday.

 A floating carbon price should be introduced in place of the proposed Emissions Reduction Fund, which is the centrepiece of the Coalition’s Direct Action climate plan, the committee recommended.

The fund, which will pay out $2.55bn over the next four years, is designed to help lower emissions by paying businesses and farmers to undertake projects which cut CO2 output or store carbon in soil and plants.

But the committee said the fund was “fundamentally flawed” in a number of ways.

The report states the plan does not have enough money to fund the abatement required for Australia to meet its 5% emissions cut, that there is no legislated limit on Australia’s emissions, no access to international emissions credits and no proper system around how to work out a business’ baseline emissions.

However, the committee was split along party lines, with Coalition senators John Williams and Anne Ruston dissenting from almost all the report’s findings.

 The two senators said Direct Action had to replace the carbon tax due to the high cost of the current policy in return for a questionable emissions cut.

“The government believes there is a better way to tackle climate change than by imposing a $7.6bn, economy-wide tax that hinders business and does nothing for the environment,” Williams and Ruston said in a statement.

“The Direct Action plan with the Emissions Reduction Fund as its centrepiece will provide incentives rather than penalties to reduce emissions: incentives for businesses to innovate and invest in new technologies, incentives to improve the efficiency and productivity of businesses’ operations and incentives to encourage farmers and landholders to store carbon on the land.”

The federal environment minister, Greg Hunt, has dismissed the findings of the report, noting that four of the six committee members are Labor or Greens senators.

“This was written by Labor and Greens senators – of course they’re going to be running a whitewash of their own policy,” he told ABC Radio.

Several independent studies of the Direct Action plan have raised doubts over whether it can meet the 5% reduction target without more funding, something the government has ruled out.

The Climate Institute has run an analysis that is critical of the Direct Action plan, but said that both Labor and the Coalition needed to increase their ambition over emissions cuts.

“Neither party can claim any climate credibility for their policies if they remain fixated on the minimum reduction effort required and not what is Australia’s fair share in avoiding the internationally agreed climate goal of avoiding two-degrees warming,” said John Connor, the chief executive of the Climate Institute.

“As one of the countries most exposed to climate risks it is in our national interest to establish credible targets.”

 Mark Butler, Labor’s environment spokesman, said expert advice heard by the committee showed that the Direct Action plan was deficient.

“After four years, three Senate inquiry hearings and two Senate estimates hearings, no one, not least the government or the Environment Department, can describe how Direct Action is going to achieve its goals,” he said.

“Direct Action is nothing more than a dressed-up slush fund with a pretty name.”

The Greens leader, Christine Milne, said: “The inquiry has made it crystal clear that Direct Action is not a viable replacement for carbon pricing and is vastly inferior to the existing law.”

“Direct Action is just a slogan. There was not a single economist in written submissions or testimony who supported Direct Action over the existing emissions trading scheme. Not Ross Garnaut, not Bernie Fraser, no one.”

Original article here

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UN climate change report card: Scientists predict Australia will continue to get hotter | ABC Radio Australia

and yet our dopey politicians are prepared to let Australia burn along with the rest of the world because taking action on climate will burn holes in the very very very large pockets of the business people who pay for their electioneering.

UN climate change report card: Scientists predict Australia will continue to get hotter | ABC Radio Australia.

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Not a pretty picture – well done world!

I’m not usually one to pay much attention to “leaked draft reports” from the IPCC because they are just drafts, but I doubt there will be many changes given the Working Group 2  ‘Impacts, Adaptation and Vulnerability’ report is due out by the end of this month. It’s not difficult to imagine that the writers for the movie “Elysium” had a sneak peak.

The Working Group II summary of thousands of peer-reviewed papers, predicts crop yields will fall by 2 per cent per decade until 2100 leading to a 20% rise in malnutrition arounfd the world.

Hundreds of millions of people are expected to be displaced, increasing the risk of violent conflict. Trillions of dollars are expected to be wiped from the global economy. Sea level rise will force mass migration across low lying areas of southern and eastern Asia raising the chances of conflict.

As usual, it will be the poor and underpriveleged who will bear the brunt of these future conditions. The wealthy, those responsible for most of the climate change, will just but their way out of trouble, like in Elysium. They should however, take heed of how that movie ends.

 

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Could a 500-house community go off-grid?

Could a 500-house community go off-grid?.

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2036: a year to fear

I have added a few pictures to this story, because I fell they tend to add something to a story that is all words. The original from Scientific American came pictureless. I’m sure they won’t mind.

Earth Will Cross the Climate Danger Threshold by 2036

Michael Mann

The rate of global temperature rise may have hit a plateau, but a climate crisis still looms in the near future.

“Temperatures have been flat for 15 years–nobody can properly explain it,” the Wall Street Journal says. “Global warming ‘pause’ may last for 20 more years, and Arctic sea ice has already started to recover,” the Daily Mail says. Such reassuring claims about climate abound in the popular media, but they are misleading at best. Global warming continues unabated, and it remains an urgent problem.

The misunderstanding stems from data showing that during the past decade there was a slowing in the rate at which the earth’s average surface temperature had been increasing. The event is commonly referred to as “the pause,” but that is a misnomer: temperatures still rose, just not as fast as during the prior decade. The important question is, What does the short-term slowdown portend for how the world may warm in the future?

The Intergovernmental Panel on Climate Change (IPCC) is charged with answering such questions. In response to the data, the IPCC in its September 2013 report lowered one aspect of its prediction for future warming. Its forecasts, released every five to seven years, drive climate policy worldwide, so even the small change raised debate over how fast the planet is warming and how much time we have to stop it. The IPCC has not yet weighed in on the impacts of the warming or how to mitigate it, which it will do in reports that were due this March and April. Yet I have done some calculations that I think can answer those questions now: If the world keeps burning fossil fuels at the current rate, it will cross a threshold into environmental ruin by 2036. The “faux pause” could buy the planet a few extra years beyond that date to reduce greenhouse gas emissions and avoid the crossover–but only a few.

A Sensitive Debate

The dramatic nature of global warming captured world attention in 2001, when the IPCC published a graph that my co-authors and I devised, which became known as the “hockey stick.” The shaft of the stick, horizontal and sloping gently downward from left to right, indicated only modest changes in Northern Hemisphere temperature for almost 1,000 years–as far back as our data went. The upturned blade of the stick, at the right, indicated an abrupt and unprecedented rise since the mid-1800s. The graph became a lightning rod in the climate change debate, and I, as a result, reluctantly became a public figure. In its September 2013 report, the IPCC extended the stick back in time, concluding that the recent warming was likely unprecedented for at least 1,400 years.

Although the earth has experienced exceptional warming over the past century, to estimate how much more will occur we need to know how temperature will respond to the ongoing human-caused rise in atmospheric greenhouse gases, primarily carbon dioxide. Scientists call this responsiveness “equilibrium climate sensitivity” (ECS). ECS is a common measure of the heating effect of greenhouse gases. It represents the warming at the earth’s surface that is expected after the concentration of CO2 in the atmosphere doubles and the climate subsequently stabilizes (reaches equilibrium).

The preindustrial level of CO2 was about 280 parts per million (ppm), so double is roughly 560 ppm. Scientists expect this doubling to occur later this century if nations continue to burn fossil fuels as they do now–the “business as usual” scenario–instead of curtailing fossil-fuel use. The more sensitive the atmosphere is to a rise in CO2, the higher the ECS, and the faster the temperature will rise. ECS is shorthand for the amount of warming expected, given a particular fossil-fuel emissions scenario.

It is difficult to determine an exact value of ECS because warming is affected by feedback mechanisms, including clouds, ice and other factors. Different modeling groups come to different conclusions on what the precise effects of these feedbacks may be. Clouds could be the most significant. They can have both a cooling effect, by blocking out incoming sunlight, and a warming effect, by absorbing some of the heat energy that the earth sends out toward space. Which of these effects dominates depends on the type, distribution and altitude of the clouds–difficult for climate models to predict. Other feedback factors relate to how much water vapor there will be in a warmer atmosphere and how fast sea ice and continental ice sheets will melt.

Because the nature of these feedback factors is uncertain, the IPCC provides a range for ECS, rather than a single number. In the September report–the IPCC’s fifth major assessment–the panel settled on a range of 1.5 to 4.5 degrees Celsius (roughly three to eight degrees Fahrenheit). The IPCC had lowered the bottom end of the range, down from the two degrees C it had set in its Fourth Assessment Report, issued in 2007. The IPCC based the lowered bound on one narrow line of evidence: the slowing of surface warming during the past decade–yes, the faux pause.

Many climate scientists–myself included–think that a single decade is too brief to accurately measure global warming and that the IPCC was unduly influenced by this one, short-term number. Furthermore, other explanations for the speed bump do not contradict the preponderance of evidence that suggests that temperatures will continue to rise. For example, the accumulated effect of volcanic eruptions during the past decade, including the Icelandic volcano with the impossible name, Eyjafjallajökull, may have had a greater cooling effect on the earth’s surface than has been accounted for in most climate model simulations. There was also a slight but measurable decrease in the sun’s output that was not taken into account in the IPCC’s simulations.

Natural variability in the amount of heat the oceans absorb may have played a role. In the latter half of the decade, La Niña conditions persisted in the eastern and central tropical Pacific, keeping global surface temperatures about 0.1 degree C colder than average–a small effect compared with long-term global warming but a substantial one over a decade. Finally, one recent study suggests that incomplete sampling of Arctic temperatures led to underestimation of how much the globe actually warmed.

New data from Cowtan & Way taking into account Arctic temperatures reveal the pause isn’t really a pause.

None of these plausible explanations would imply that climate is less sensitive to greenhouse gases. Other measurements also do not support the IPCC’s revised lower bound of 1.5 degrees C. When all the forms of evidence are combined, they point to a most likely value for ECS that is close to three degrees C. And as it turns out, the climate models the IPCC actually used in its Fifth Assessment Report imply an even higher value of 3.2 degrees C. The IPCC’s lower bound for ECS, in other words, probably does not have much significance for future world climate–and neither does the faux pause.

For argument’s sake, however, let us take the pause at face value. What would it mean if the actual ECS were half a degree lower than previously thought? Would it change the risks presented by business-as-usual fossil-fuel burning? How quickly would the earth cross the critical threshold?

A Date with Destiny: 2036

Most scientists concur that two degrees C of warming above the temperature during preindustrial time would harm all sectors of civilization–food, water, health, land, national security, energy and economic prosperity. ECS is a guide to when that will happen if we continue emitting CO2 at our business-as-usual pace.

I recently calculated hypothetical future temperatures by plugging different ECS values into a so-called energy balance model, which scientists use to investigate possible climate scenarios. The computer model determines how the average surface temperature responds to changing natural factors, such as volcanoes and the sun, and human factors–greenhouse gases, aerosol pollutants, and so on. (Although climate models have critics, they reflect our best ability to describe how the climate system works, based on physics, chemistry and biology. And they have a proved track record: for example, the actual warming in recent years was accurately predicted by the models decades ago.)

I then instructed the model to project forward under the assumption of business-as-usual greenhouse gas emissions. I ran the model again and again, for ECS values ranging from the IPCC’s lower bound (1.5 degrees C) to its upper bound (4.5 degrees C). The curves for an ECS of 2.5 degrees and three degrees C fit the instrument readings most closely. The curves for a substantially lower (1.5 degrees C) and higher (4.5 degrees C) ECS did not fit the recent instrumental record at all, reinforcing the notion that they are not realistic.

To my wonder, I found that for an ECS of three degrees C, our planet would cross the dangerous warming threshold of two degrees C in 2036, only 22 years from now. When I considered the lower ECS value of 2.5 degrees C, the world would cross the threshold in 2046, just 10 years later [see graph on pages 78 and 79].

So even if we accept a lower ECS value, it hardly signals the end of global warming or even a pause. Instead it simply buys us a little bit of time–potentially valuable time–to prevent our planet from crossing the threshold.

Cautious Optimism

These findings have implications for what we all must do to prevent disaster. An ECS of three degrees C means that if we are to limit global warming to below two degrees C forever, we need to keep CO2 concentrations far below twice preindustrial levels, closer to 450 ppm. Ironically, if the world burns significantly less coal, that would lessen CO2 emissions but also reduce aerosols in the atmosphere that block the sun (such as sulfate particulates), so we would have to limit CO2 to below roughly 405 ppm.

We are well on our way to surpassing these limits. In 2013 atmospheric CO2 briefly reached 400 ppm for the first time in recorded history–and perhaps for the first time in millions of years, according to geologic evidence. To avoid breaching the 405-ppm threshold, fossil-fuel burning would essentially have to cease immediately. To avoid the 450-ppm threshold, global carbon emissions could rise only for a few more years and then would have to ramp down by several percent a year. That is a tall task. If the ECS is indeed 2.5 degrees C, it will make that goal a bit easier.

Even so, there is considerable reason for concern. The conclusion that limiting CO2 below 450 ppm will prevent warming beyond two degrees C is based on a conservative definition of climate sensitivity that considers only the so-called fast feedbacks in the climate system, such as changes in clouds, water vapor and melting sea ice. Some climate scientists, including James E. Hansen, former head of the nasa Goddard Institute for Space Studies, say we must also consider slower feedbacks such as changes in the continental ice sheets. When these are taken into account, Hansen and others maintain, we need to get back down to the lower level of CO2 that existed during the mid-20th century–about 350 ppm. That would require widespread deployment of expensive “air capture” technology that actively removes CO2 from the atmosphere.

Furthermore, the notion that two degrees C of warming is a “safe” limit is subjective. It is based on when most of the globe will be exposed to potentially irreversible climate changes. Yet destructive change has already arrived in some regions. In the Arctic, loss of sea ice and thawing permafrost are wreaking havoc on indigenous peoples and ecosystems. In low-lying island nations, land and freshwater are disappearing because of rising sea levels and erosion. For these regions, current warming, and the further warming (at least 0.5 degree C) guaranteed by CO2 already emitted, constitutes damaging climate change today.

Let us hope that a lower climate sensitivity of 2.5 degrees C turns out to be correct. If so, it offers cautious optimism. It provides encouragement that we can avert irreparable harm to our planet. That is, if–and only if–we accept the urgency of making a transition away from our reliance on fossil fuels for energy.

Original article here

 

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