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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Explaining climate change science & rebutting global warming misinformation

Scientific skepticism is healthy. Scientists should always challenge themselves to improve their understanding. Yet this isn't what happens with climate change denial. Skeptics vigorously criticise any evidence that supports man-made global warming and yet embrace any argument, op-ed, blog or study that purports to refute global warming. This website gets skeptical about global warming skepticism. Do their arguments have any scientific basis? What does the peer reviewed scientific literature say?

 


Why we need to talk about the scientific consensus on climate change

Posted on 20 November 2014 by John Cook

An interesting sequence of events followed the publication of a scientific paper the Skeptical Science team published in May last year. The paper found a 97% consensus that humans were causing global warming in relevant scientific papers. Finding an overwhelming consensus was nothing new. Studies in 2009 and 2010 also found 97% agreement among climate scientists on human-caused global warming. Nevertheless, the paper attracted much media attention, including tweets from Elon Musk and President Obama.

We expected our work would be attacked from those who reject climate science. We weren’t disappointed. Since publication, hundreds of blog posts, reports, videos, papers and op-eds have been published attacking our paper. A year and a half later, there is no sign of slowing. But this is just the latest chapter in over two decades of manufactured doubt on the scientific consensus about climate change.

What did surprise me were criticisms from scientists who accept the science on climate change. They weren’t arguing against the existence of a consensus, but whether we should be communicating the consensus. This surprised me, as our approach to climate communication was evidence-based, drawing on social science research. So in response, I along with co-author Peter Jacobs have published a scholarly paper summarising all the evidence and research underscoring the importance of consensus messaging.

One objection against consensus messaging is that scientists should be talking about evidence, rather than consensus. After all, our understanding of climate change is based on empirical measurements, not a show of hands. But this objection misunderstands the point of consensus messaging. It’s not about “proving” human-caused global warming. It’s about expressing the state of scientific understanding of climate change, which is built on a growing body of evidence.

Consensus messaging recognises the fact that people rely on expert opinion when it comes to complex scientific issues. Studies in 2011 and 2013 found that perception of scientific consensus is a gateway belief that has a flow-on effect to a number of other beliefs and attitudes. When people are aware of the high level of scientific agreement on human-caused global warming, they’re more likely to accept that climate change is happening, that humans are causing it and support policies to reduce carbon pollution.

Another argument against consensus messaging is that public understanding of the climate issue has moved on from fundamental issues such as the consensus. The evidence says otherwise. Public surveys have found that the public are deeply unaware of the consensus. On average, the public think there’s a 50:50 debate. There are several contributors to this “consensus gap”, including mainstream media’s tendency to give contrarian voices equal weight with the climate science community.

Funnily enough, a third objection to consensus messaging argues that we shouldn’t communicate consensus because public views have not moved on. In other words, the fact that public opinion about consensus hasn’t shifted over the last decade implies that consensus messaging is ineffective.

Dan Kahan argues that consensus is a polarizing message. Liberals are predisposed to respond positively to consensus messaging. Meanwhile, conservatives are more likely to reject the scientific consensus.

Political ideology certainly does influence people’s attitudes towards climate change. The following graph shows data I’ve collected from a representative sample of Americans, asking them how many climate scientists agreed about human-caused global warming. The horizontal access in this graph represents political ideology (specifically, support for an unregulated free market, free of interference from government).

These data come from research by John Cook, taken from a survey of a US representative sample (N=200).

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40 comments


2014 SkS Weekly News Roundup #47A

Posted on 19 November 2014 by John Hartz

A carbon tax could bolster wobbly progress in renewable energy

A couple of years ago, the smart money was on wind. In 2012, 13 gigawatts worth of wind-powered electricity generation capacity was installed in the United States, enough to meet the needs of roughly three million homes. That was some 40 percent of all the capacity added to the nation’s power grid that year, up from seven gigawatts added in 2011 and just over five in 2010.

But then a federal subsidy ended. Only one gigawatt worth of wind power capacity was installed in 2013. In the first half of 2014, additions totaled0.835 gigawatts. Facing a Congress controlled by Republicans with little interest in renewable energy, wind power’s future suddenly appears much more uncertain.

“Wind is competitive in more and more markets,” said Letha Tawney at the World Resources Institute. “But any time there is uncertainty about the production tax credit, it all stops.” 

A Carbon Tax Could Bolster Wobbly Progress in Renewable Energy by Eduardo Porter, New York Times, Nov 18, 2014

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3 comments


Turbulent week for global climate policy leaves many questions

Posted on 19 November 2014 by Guest Author

They came, they saw, they cuddled koalas and world leaders then largely ignored the Australian Prime Minister Tony Abbott’s instructions to ignore the global, intergenerational and morally challenging kerfuffle over climate change.

All in all the last seven days have proven to be momentous for climate change policy - both at the Brisbane G20 summit in Queensland and elsewhere.

Suspicions were confirmed, deals were announced and positions were galvanized, but there are still major questions as the world tries to find a safe route to a new global deal to cut greenhouse gas emissions.

I’ve been doing a bit of unpicking. Here are the threads.

Abbott coal’s great defender

It’s hard to think of a sterner test of Tony Abbott’s resolve to be the coal industry’s great international defender as that which he faced in Brisbane.

In the run up to the meeting, the world’s two largest emitters of greenhouse gas emissions, the United States and China, announced what many described as a “historic” agreement to kerb emissions (more on this in a bit).

As the host of the G20, Australia had already faced concerted pressure both behind the scenes and in front of them to make climate change a more central part of the meeting’s agenda.

When the US President Barack Obama finally arrived in Brisbane, he headed to the University of Queensland to deliver a speech where he called on other leaders to deliver a strong global agreement next year in Paris.

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1 comments


President Obama's climate leadership faces the Keystone XL challenge

Posted on 18 November 2014 by John Abraham

What a change a few years makes. For those of us concerned about climate change, seven years ago marked a low-point. It was a time where no meaningful actions had been taken to reduce carbon pollution and prepare our nation and the world for the threat of global warming. Now, we celebrate a series of major plans and actions that have the potential for helping us avoid the worst climate risks.

These past years have cemented Obama’s legacy as a climate-aware president. They have also cemented the opposition (as if more cement was needed) as either too weak-minded to understand basic physics or too cowardly, favoring political expediency over the fate of future generations. This is one of those issues on which history books hinge. This was the time the USA took a leadership role to simultaneously reduce carbon pollution, adapt to the unavoidable changes in the pipeline, and build the energy infrastructure to lead in the future’s energy economy.

What actions has the Obama administration taken? We can remember back to the increase in fuel efficiency standards for passenger vehicles and finalization of standards for commercial vehicles. These standards not only reduce carbon emissions but they lower costs to consumers and preserve the valuable resource petroleum.

Perhaps the most significant actions taken by the administration deal with pollution from existing and new coal power plants. The Environmental Protection Agency has developed a Clean Power Plant to reduce power-plant emissions. The plan allows flexibility in meeting emission reductions reflecting different conditions and power-portfolios across the country.

The administration has set forth an international agreement to reduce very potent greenhouse gases called hydrofluorocarbons. This agreement was exciting because it gave lie to the idea that USA action would put as at an economic disadvantage. What this agreement showed is that when the USA acts, other countries follow.

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39 comments


Just how ‘Sapiens’ in the world of high CO2 concentrations?

Posted on 17 November 2014 by Marcin Popkiewicz

High concentration of CO2 reduces man's intellectual abilities

Did you ever experience being at a lecture or a meeting in a room where you felt tired, your eyes were closing and no matter how hard you tried you could not concentrate? The reason did not have to be a boring subject or a mediocre lecturer – it is a common experience caused by high concentration of carbon dioxide in the air of a crowded and poorly ventilated conference room or a classroom.

People exhale carbon dioxide. If the room is crowded, small and poorly ventilated, the concentration of carbon dioxide in the air grows. When in turn we inhale such air, the carbon dioxide contained in it gets dissolved in our blood and reacts with water to create carbonic acid [H2CO3], which, in turn dissolves into ions of hydrogen [H+] and bicarbonate [HCO3]. Increase in the concentration of hydrogen ions increases blood acidity and creates electrolyte imbalance, causing increased discomfort and decline in intellectual performance. We feel tired, numb and less capable of any mental or physical effort.

Blood pH vs CO2 concentration

Figure 1. Changes in blood acidity level (pH coefficient) as  a function of CO2 concentration in the air we breathe (expressed in number of CO2 molecules per million - ppm). Increase of CO2 concentration in the atmosphere from 280 ppm in the preindustrial era to the current approximately 400 ppm reduces pH of our blood by 0.1 (which is equivalent to acidity increase by 30%). Effective ventilation of buildings becomes more difficult (D. Robertson, 2006).

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32 comments


2014 SkS Weekly Digest #46

Posted on 16 November 2014 by John Hartz

SkS Highlights

Speaking at the University of Queensland, the President of the United States, Barack Obama, reminded his audience of college and high school students that he had tweeted about The Consensus Project (TCP) last year. Here are the President's words:

This university is recognized as one of the world’s great institutions of science and teaching.  Your research led to the vaccine that protects women and girls around the world from cervical cancer.  Your innovations have transformed how we treat disease and how we unlock new discoveries.  Your studies have warned the world about the urgent threat of climate change.  In fact, last year I even tweeted one of your studies to my 31 million followers on Twitter.  (Laughter.)  Just bragging a little bit.  (Applause.)  I don’t think that’s quite as much as Lady Gaga, but it’s pretty good.  (Laughter.)  That’s still not bad.

Remarks by President Obama at the University of Queensland, White House Briefing Room, Nov 15, 2014

Click here to access a video of President Obama's address.

Toon of the Week

2014 Toon 46 

h/t to I Heart Climate Scientists

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2 comments


2014 SkS Weekly News Roundup #46B

Posted on 15 November 2014 by John Hartz

4 reasons Republicans are losing their sh*t over the climate deal

Republican Senate Leader Mitch McConnell of Kentucky is not pleased about the historic joint announcement of planned carbon emission limits by the U.S. and China. He put out this statement Wednesday:

Our economy can’t take the President’s ideological War on Coal that will increase the squeeze on middle-class families and struggling miners. This unrealistic plan, that the President would dump on his successor, would ensure higher utility rates and far fewer jobs. The President said his policies were on the ballot, and the American people spoke up against them. It’s time for more listening, and less job-destroying red tape. Easing the burden already created by EPA regulations will continue to be a priority for me in the new Congress.

McConnell has frequently complained that reducing our emissions is pointless if other countries won’t do the same. Just last month, explaining why the EPA’s proposed power plant regulations are all pain and no gain, he said, “nobody else is going to do that. The Indians and Chinese are building coal plants.”

4 reasons Republicans are losing their sh*t over the U.S.-China climate deal by Ben Adler, Grist, Nov 12, 2014

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1 comments


Fact check: China pledged bigger climate action than the USA; Republican leaders wrong

Posted on 14 November 2014 by dana1981

This week, President Barack Obama and Chinese President Xi Jinping unveiled a secretly negotiated agreement for both countries to slow global warming by pledging to reduce carbon pollution. Specifically, President Obama pledged that the USA would cut its carbon pollution 26–28% below 2005 levels by 2025, while President Xi pledged that by 2030, Chinese carbon pollution will peak and 20% of the country’s energy will come from low-carbon sources.

This agreement received predominantly high praise because it represents the world’s two biggest net carbon polluters taking a leading role in committing to tackle the threats posed by human-caused global warming. China in particular is often used as an excuse by those in the United States and around the world who oppose taking steps to slow global warming.

With the announcement of this agreement, the Chinese president has agreed that his country must begin the process of slowing the growth of and eventually reducing its carbon pollution. The common refrain “nothing we do matters unless China acts” is moot.

However, Republican House Majority Leader John Boehner and soon-to-be Senate Majority Leader Mitch McConnell were among the few who issued negative public statements about the climate agreement. McConnell in particular badly misunderstood the practical consequences of the Chinese and American carbon pledges, saying,

As I read the agreement it requires the Chinese to do nothing at all for 16 years while these carbon emissions regulations are creating havoc in my state and around the country,

Senator McConnell misunderstood the Chinese target of reaching peak carbon pollution levels by 2030 as a pledge to “do nothing.” In reality, China has been developing rapidly with hundreds of millions of citizens rising out of poverty, thus demanding more energy. Much of that demand has been met with new coal power plants; China has added one and a half times the entire US coal power plant fleet in just the past decade. As a result, Chinese carbon pollution has been rising fast.

China could not meet its climate pledge by maintaining business-as-usual (BAU) and doing “nothing.” Quite the opposite; curbing those rising carbon emissions as China’s economy continues to grow will require substantial effort. That’s why President Xi also pledged that 20% of the country’s energy would come from low-carbon sources by 2030.

In comparison, the United States will have a relatively easy time meeting the pledge made by President Obama. US carbon pollution is already about 10–15% below 2005 levels and falling by about 1.5% per year. Achieving the target of 26–28% emissions cuts below 2005 levels by 2025 will only require continuing the current rate at which American carbon pollution is already falling.

China and USA carbon dioxide emissions from power generation from 1981 to 2012 (solid lines and squares; data from US Energy Information Administration), pledges (dotted lines), and business-as-usual (BAU) emissions (dashed lines).

China and USA carbon dioxide emissions from power generation from 1981 to 2012 (solid lines and squares; data from US Energy Information Administration), pledges (dotted lines), and business-as-usual (BAU) emissions (dashed lines). Created by Dana Nuccitelli.

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26 comments


New study shows warm waters are melting Antarctica from below

Posted on 13 November 2014 by John Abraham

Just this week, a new study has appeared which describes a clever method for measuring the flows of ocean currents and their impacts on ice shelves. This study has identified a major mechanism for melting ice in the Southern Hemisphere.

The paper, co-authored by Andrew Thompson, Karen Heywood, and colleagues is very novel. The scientists used sea gliders to identify water flows that bring warm waters to the base of ice shelves in Antarctica. As I’ve written before, ocean currents are complex; you cannot neglect their impact on the Earth’s climate.

In some parts of the ocean, dense waters near the surface fall to the ocean floor and spread across the globe. In other regions, waters from the deep rise to the surface. Similarly, waters move horizontally and carry their heat with them. In some cases the surface waters and the mid-depth waters flow in different directions.

But regardless of the direction of flow, these waters carry energy with them. This process, often called “advection,” results in a major redistribution of heat across the globe. Sometimes, warm waters flow into cold regions, transferring heat, and melting ice. It is this phenomenon that was at the center of the current paper.

Fluids sometimes move as large directional masses (sometimes called bulk motion) caused by some agent of motion, for instance winds that blow over the surface and drag waters. Other motions are characterized by swirls and eddies – not unidirectional flow. This type of motions is called eddy-induced transport. A determination of which type of transport dominates and where they dominate is important to understanding Antarctic ice melt.

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9 comments


2014 SkS Weekly News Roundup #46A

Posted on 12 November 2014 by John Hartz

A tricky transition from fossil fuel

Denmark, a tiny country on the northern fringe of Europe, is pursuing the world’s most ambitious policy against climate change. It aims to end the burning of fossil fuels in any form by 2050 — not just in electricity production, as some other countries hope to do, but in transportation as well.

Now a question is coming into focus: Can Denmark keep the lights on as it chases that lofty goal?

Lest anyone consider such a sweeping transition to be impossible in principle, the Danes beg to differ. They essentially invented the modern wind-power industry, and have pursued it more avidly than any country. They are above 40 percent renewable power on their electric grid, aiming toward 50 percent by 2020. The political consensus here to keep pushing is all but unanimous.

A Tricky Transition From Fossil Fuel: Denmark Aims for 100 Percent Renewable Energy by Justin Gillis, New York Times, Nov 10, 2014

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Remote-control robots reveal why the Antarctic ice sheet is melting

Posted on 12 November 2014 by Guest Author

This article was originally posted on The Carbon Brief on Nov 10, 2014

by Robert McSweeney

Antarctic Research Ship

At current rates, ice sheet loss will become the most significant  contributor to global sea level rise during this century, yet there is still a lot that scientists  don't know about the underlying causes. This is partly because Antarctica is such a difficult place to take measurements.

But now robotic underwater gliders are giving scientists new insight into why the Antarctic ice sheet is melting.

Ice sheets

An ice sheet is a huge layer of ice that sits on land. The two on the Earth today are found on Antarctica and Greenland, but in the last ice age there were also ice sheets on North America and northern Europe.

The Antarctic ice sheet spans more than 14 million square kilometers, which is roughly the same size as the US and Mexico put together. The ice sheet also spills out onto the surrounding ocean in the form of ice shelves.

The Intergovernmental Panel on Climate Change (IPCC)  estimates that the Antarctic ice sheet is currently losing around 150 billion tonnes of ice per year. One of the main areas of ice loss is from the Antarctic Peninsula, shown in the red rectangle in the map below.

Map of Antarctica 

Map of Antarctica. Antarctic Peninsula shown in red rectangle. Creative Commons.

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More research confirming large methane leakage from shale boom

Posted on 11 November 2014 by gws

More research published in 2014 is consistent with the previous notion that the shale boom in the US has been, and likely still is, causing much larger fugitive methane (and higher hydrocarbon) emissions than claimed by the industry.

In a recent publication in Earth's Future, a new journal published by the American Geophysical Union (AGU) dedicated to "global change and sustainability", a German-US team of researchers showed increasing atmospheric methane abundances over two rapidly developing shale areas, the Bakken and Eagle Ford shales in North Dakota and south Texas, respectively. Their methane emissions estimate is based on the difference in atmospheric methane in these areas between the years prior said rapid development, 2006-2008, and during it, 2009-2011.

Mapping methane anomalies

Data for the authors' analyses came from the European Space Agency (ESA) ENVISAT's instrument SCIAMACHY, and is unfortunately not available beyond early 2012, when contact with the satellite was lost. The instrument measured the total amount of methane in the atmosphere, the overwhelming amount of which is in the lower 10-12 km, the troposphere. Based on the resolution of the instrument, and the amount of time the satellite spent overhead, the authors used 3 years of data to get high enough precision for their study. They also accounted for how winds displaced the emitted methane differently between the two study periods. The result is depicted in Figure 1 below.

 

Fig. 4 from Schneisinger et al

Figure 1: Shown are two latitude-longitude maps of the difference in atmospheric methane abundance (expressed as a mole fraction), or  methane anomaly, for the period 2009–2011 relative to the period 2006–2008. The locations of oil and gas wells are shown in pink. The regions used to estimate shale area emissions are red-rimmed. The corresponding regions used to determine the background values are framed by the green dashed lines. Averaged near-surface wind differences between the periods are illustrated by dark grey arrows.

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We must manage global warming risks by cutting carbon pollution, top scientists conclude

Posted on 10 November 2014 by dana1981

Last week, the Intergovernmental Panel on Climate Change (IPCC) published its latest Synthesis Report, summarizing the scientific research on the causes and impacts of global warming, and how we can mitigate its consequences. The report included various graphs showing how we’re changing the Earth’s climate, and concluded that humans are causing rapid and dangerous global warming.

Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.

Much of the report focused on the risks associated with these rapid climate changes. Fundamentally, climate change is a risk management problem. Even if you’re sceptical of the vast body of scientific research pointing to dangerous and potentially catastrophic climate change, there’s a very good chance the experts and their supporting evidence are correct and your scepticism is misplaced. The IPCC report put those risks into perspective,

Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. Limiting climate change would require substantial and sustained reductions in greenhouse gas emissions which, together with adaptation, can limit climate change risks.

Many aspects of climate change and associated impacts will continue for centuries, even if anthropogenic emissions of greenhouse gases are stopped. The risks of abrupt or irreversible changes increase as the magnitude of the warming increases.

The key word here is “irreversible,” and it’s used 14 times in the IPCC’s latest Summary for Policymakers. For example, if ice sheets in Greenland and Antarctica collapse into the ocean, as they’ve already begun to, we can’t take the ice out of the ocean and put it back on land. That lost ice and the sea level rise it causes are irreversible impacts.

Conversely, policies to slow global warming are reversible. A new study by scientists at Duke University found that the widespread rejection of climate science by American political conservatives is in large part due to their distaste for the proposed solutions. Climate contrarians are afraid that climate policies will slow economic growth, despite evidence to the contrary.

However, if it turns out that the sceptics are right in their optimism that the best case climate scenario will occur, and if we go too far in our efforts to reduce carbon pollution, we can easily scale those efforts back. We can’t reanimate extinct species, but we can adjust climate policies as needed.

Speaking of species extinctions, the IPCC discussed that serious threat as well,

A large fraction of species face increased extinction risk due to climate change during and beyond the 21st century, especially as climate change interacts with other stressors (high confidence). Most plant species cannot naturally shift their geographical ranges sufficiently fast to keep up with current and high projected rates of climate change in most landscapes; most small mammals and freshwater molluscs will not be able to keep up at the rates projected under RCP4.5 and above in flat landscapes in this century (high confidence).

Marine species are also at risk due to the dual threats of warming oceans and ocean acidification, both of which are caused by carbon pollution from burning fossil fuels.

Since the beginning of the industrial era, oceanic uptake of CO2 has resulted in acidification of the ocean; the pH of ocean surface water has decreased by 0.1 (high confidence), corresponding to a 26% increase in acidity

The IPCC concluded that if we take serious action to reduce fossil fuel consumption and greenhouse gas emissions, we can limit the future increase in ocean acidity to about 16%. If we continue on a business-as-usual fossil fuel dependent path, ocean acidity will increase by around 100%, with dire consequences for marine ecosystems. This will also hurt our fisheries and contribute to food insecurity.

Climate change is projected to undermine food security (Figure SPM.9). Due to projected climate change by the mid-21st century and beyond, global marine species redistribution and marine biodiversity reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services (high confidence) ... Global temperature increases of ~4°C or more14 above late-20th century levels, combined with increasing food demand, would pose large risks to food security globally (high confidence).

As these figure below from the report also illustrates, about 70% of studies indicate that crop yields will decline as the Earth continues to warm after 2030, with a high chance that yields could decline by 25% or more by the end of the century if we continue on our current path.

Summary of projected changes in crop yields, due to climate change over the 21st century. Yellow indicates studies that project crop yield decreases, blue indicates studies projecting increases. Summary of projected changes in crop yields, due to climate change over the 21st century. Yellow indicates studies that project crop yield decreases, blue indicates studies projecting increases. Illustration: IPCC AR5

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2014 SkS Weekly Digest #45

Posted on 9 November 2014 by John Hartz

SkS Highlights

The 2014 SkS Weekly News Roundup #45B attracted the highest number of comments of the items posted on SkS during the past week. Dana's article, Weather Channel co-founder John Coleman prefers conspiracies to climate science garnered the second highest number.

Toon of the Week

 2014 Toon 45

See: Voters put climate change policy in the hands of climate change denier by David Horsey, Los Angeles Times, Nov 7, 2014

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4 comments


2014 SkS Weekly News Roundup #45C

Posted on 8 November 2014 by John Hartz

Biggest Brazil metro area desperate for water

It’s been nearly a month since Diomar Pereira has had running water at his home in Itu, a commuter city outside Sao Paulo that is at the epicenter of the worst drought to hit southeastern Brazil in more than eight decades.

Like others in this city whose indigenous name means “big waterfall,” Pereira must scramble to find water for drinking, bathing and cooking. On a recent day when temperatures hit 90 degrees (32 Celsius), he drove to a community kiosk where people with empty soda bottles and jugs lined up to use a water spigot. Pereira filled several 13-gallon containers, which he loaded into his Volkswagen bug.

“I have a job and five children to raise and am always in a rush to find water so we can bathe,” said Pereira, a truck driver who makes the trip to get water every couple of days. “It’s very little water for a lot of people.”

Biggest Brazil metro area desperate for water, AP/Washington Post, Nov 7, 2014

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New study questions the accuracy of satellite atmospheric temperature estimates

Posted on 7 November 2014 by John Abraham

Over the past decades, scientists have made many measurements across the globe to characterize how fast the Earth is warming. It may seem trivial, but taking the Earth’s temperature is not very straightforward. You could use temperature thermometers at weather stations that are spread across the globe. Measurements can be taken daily and information sent to central repositories where some average is determined.

A downside of thermometers is that they do not cover the entire planet – large polar regions, oceans, and areas in the developing world have no or very few measurements. Another problem is that they may change over time. Perhaps the thermometers are replaced or moved, or perhaps the landscape around the thermometers changes which could impact the reading. And of course, measurements of the ocean regions are a whole other story.

An alternative technique is to use satellites to extract temperatures from radiative emission at microwave frequencies from oxygen in the atmosphere. Satellites can cover the entire globe and thereby avoid the problem with discrete sensors. However, satellites also change over time, their orbit can change, or their detection devices can also change.

Another issue with satellites is that the measurements are made throughout the atmosphere that can contain contaminants to corrupt the measurement. For instance, it is possible that water droplets (either in clouds or precipitation) can influence the temperature readings.

So, it is clear that there are strengths and weaknesses to any temperature measurement method. You would hope that either method would tell a similar story, and they do to some extent, but there are key differences. Basically, the lower atmosphere (troposphere) is heating slower than the Earth surface.

In fact, for the time period 1987–2006, the temperatures among the four groups that collect satellite data ranges from 0.086°C per decade to 0.22°C per decade. In more recent years, the trend is much reduced, and for two of the leading satellite groups (University of Alabama at Huntsville and Remote Sensing Systems), temperatures are basically flat.

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2014 SkS Weekly News Roundup #45B

Posted on 6 November 2014 by John Hartz

Britain had one of warmest and wettest years on record

The UK is on course to experience the warmest and one of the wettest years since records began more than a century ago, feeding fears that future droughts and flash floods could cost lives.

Figures from the Met Office show January to October has been the warmest since records began in 1910, and also the second-wettest. Unless November and December are extremely cold, 2014 will be the hottest year on record.

Experts say this the result of climate change, which they warn could place a burden on the NHS as Britons struggling to cope with future heatwaves end up in hospital. 

Britain had one of warmest and wettest years on record by Press Association/The Guardian, Nov 4, 2014

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Looking after the right forests benefits the climate

Posted on 6 November 2014 by MarkR

Dr Nadine Unger and other forest-science experts (here and at RealClimate) have recently written about whether saving forests will reduce future climate change. Dr Unger mentions a recent "landmark deal" on sustainable forestry and suggests it's a "bad bet", the others disagree.

I'm convinced that it's a very good bet. If we want to limit global warming, then we have a carbon budget that we can spend, and we can spend this budget by chopping down trees or by doing other things like burning oil and gas. The "landmark deal" aims to keep carbon locked up in forests, clearing space in the budget. Dr Unger argues that planting trees doesn't always help the climate, but her technical points are not really relevant to the tropical forests covered in this particular "landmark deal".

Trees and Temperatures

One way in which trees affect temperatures is that they tend to be darker than grasses or snow. Just like how a black car feels hot to the touch on a bright, sunny day, trees absorb extra heat and warm up. 

This is balanced by how they absorb carbon. Clearing forests releases this carbon (mostly) as carbon dioxide (CO2), a warming greenhouse gas. There are other processes too, and researchers have calculated the total effect that forests have on temperatures. Dr Unger mentions the surprising result that planting trees in colder areas can boost warming (e.g. Bonan et al., 2008).

However, tropical forests are very dense. Powered by bright sunlight year round and fuelled by heavy rainfall, they suck up enormous amounts of carbon. There's wide agreement that they have an overall cooling effect, and one of Dr Unger's own references (Jackson et al., 2008) states straight up that "Tropical projects—avoided deforestation, forest restoration, and afforestation—provide the greatest climate value".

In general, one of Dr Unger's points is that in many developed countries, like the US and UK, planting trees isn't going to help reduce global warming. This is probably true, but not relevant for the "landmark deal" under discussion. This is about Reducing Emissions from Deforestation and Forest Degradation (REDD+) in Developing Countries (more details are in a note that I researched and wrote for the UK Parliament).

Here's a map of countries doing REDD+ projects. It's dominated by tropical forests in countries like Brazil, Peru and Indonesia.

Figure 1 Map of countries with current REDD+ projects, darker shade means that the country has more projects. Modified from this map, produced by CIFOR.

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5 comments


2014 SkS Weekly News Roundup #45A

Posted on 4 November 2014 by John Hartz

29 bullets tell all about climate challenge

The results are in. Yesterday the United Nations Intergovernmental Panel on Climate Change released it final report crystallizing 13 months of work by more than 800 scientists. The “synthesis report” gives a no-nonsense assessment of how the climate is changing, what is causing the change, the impacts the changes will have on us and the planet, and the “mitigation” steps we should take to prevent the impacts from getting worse. The recommendations are intended first and foremost for national leaders, who in 2015 will make what may be a last-chance effort to reach a binding global climate treaty.

Although the report’s authors try to give a condensed snapshot of the most important data and recommendations, the document still clocks in at 116 pages. I will attempt, here, to capture what you need to know most, in 29 bullets. Forgive the staccato.

29 bullets tell all about climate challenge by Mrak Frischetti, Scientific American, Nov 3, 2014

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Concluding instalment of the Fifth IPCC Assessment Report:

Posted on 4 November 2014 by John Hartz

This article is a reprint of a press release posted by the Intergovernmental Panel on Climate Change on Nov 2, 2014

Climate change threatens irreversible and dangerous impacts, but options exist to limit its effects

COPENHAGEN, Nov 2 – Human influence on the climate system is clear and growing, with impacts observed on all continents. If left unchecked, climate change will increase the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. However, options are available to adapt to climate change and implementing stringent mitigations activities can ensure that the impacts of climate change remain within a manageable range, creating a brighter and more sustainable future.

AR5: Synthesis Report Cover

These are among the key findings of the Synthesis Report (long version)/Synthesis Report (approved summary for policymakers) released by the Intergovernmental Panel on Climate Change (IPCC) on Sunday. The Synthesis Report distils and integrates the findings of the IPCC Fifth Assessment Report produced by over 800 scientists and released over the past 13 months – the most comprehensive assessment of climate change ever undertaken.

“We have the means to limit climate change,” said R. K. Pachauri, Chair of the IPCC. “The solutions are many and allow for continued economic and human development. All we need is the will to change, which we trust will be motivated by knowledge and an understanding of the science of climate change.”

The Synthesis Report confirms that climate change is being registered around the world and warming of the climate system is unequivocal. Since the 1950s many of the observed changes are unprecedented over decades to millennia. “Our assessment finds that the atmosphere and oceans have warmed, the amount of snow and ice has diminished, sea level has risen and the concentration of carbon dioxide has increased to a level unprecedented in at least the last 800,000 years,” said Thomas Stocker, Co-Chair of IPCC Working Group I.

The report expresses with greater certainty than in previous assessments the fact that emissions of greenhouse gases and other anthropogenic drivers have been the dominant cause of observed warming since the mid-20th century.

The impacts of climate change have already been felt in recent decades on all continents and across the oceans.

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