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Climate Hustle

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?

 


2016 SkS Weekly News Roundup #30

Posted on 23 July 2016 by John Hartz

A chronological listing of the news articles posted on the Skeptical Science Facebook page during the past week.

Sun July 17, 2016

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Study links heatwave deaths in London and Paris to climate change

Posted on 22 July 2016 by Guest Author

This is a re-post from Carbon Brief by Robert McSweeney

In 2003, more than 70,000 people across Europe died in a sweltering heatwave that spanned much of the summer.

France was among the worst-affected countries, with 15,000 deaths in August alone. In the UK, the summer saw more than 2,000 heat-related fatalities.

A new first-of-a-kind study works out how many of the deaths in Paris and London are down to the heatwave being intensified by human-caused climate change.

The findings suggest that 506 of the 735 summer fatalities in Paris in 2003, and 64 of the 315 in London, were a result of human influence on the climate.

Human influence

The European summer heatwave of 2003 has been something of a focal point for scientists looking at if and how human-caused climate change influences extreme weather events.

In 2004, the heatwave was the subject of the first ever attribution study, which found that climate warming from human activity had at least doubled the likelihood of such an event. In 2014, another study found that a similar “extremely hot” summer in Europe has become 10 times more likely over the last 10-15 years because of climate change.

Taking this a step further, the new study, published in Environmental Research Letters, attributes the number of deaths during the 2003 heatwave to our warming climate.

The study makes use of the weather@home project, where members of the public offer spare capacity on their home computers for scientists to run model simulations.

The researchers ran thousands of simulations of European weather in 2003. One set of model runs simulated the weather according to the climate as it was – i.e. in a world warmed by past greenhouse gas emissions. The second set simulated the weather in a hypothetical world with no human influences on climate.

The researchers then compared the heat and humidity between the hypothetical world and the one better matched to reality to see how they affect the number of premature deaths in the summer of the same year. Lead author Dr Daniel Mitchell, a researcher in the Department of Physics at the University of Oxford, explains to Carbon Brief:

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The best strategies to keep bodies cool in a heatwave, according to researchers

Posted on 21 July 2016 by John Abraham

As we hit high-heat season in the Northern Hemisphere, it is useful to clarify tactics that can be used to help maintain healthy body temperatures. These tips are not commonly known and can be adopted by anyone, anywhere. While I am a climate scientist, my funded work is in the area of heat transfer, particularly in the human body. I work with medical companies to maintain healthy body temperatures during surgeries or other situations. I also deal with scald burns and I often serve in burn injury litigation.

Here are some key tips. First, avoid hyperthermia in the first place – drink plenty of fluids, avoiding direct sunlight, trying to get a respite from heat each day, avoiding physical exertion during the hottest parts of the day are all great suggestions. But, if you need to lower a body temperature, Dr. Robert Huggins, VP of Research and Athlete Performance at the Korey Stringer Institute suggests:

The general rule is to cool as much of the body’s surface as possible …. the larger the area you cool and the colder the device you use to cool it the faster the cooling rate. An appropriate goal is to use a method that cools at a rate of 0.15°C per minute. This can typically be achieved by immersion techniques using a tub or other basin filled with ice cold water or via rotating cold ice towels over the body.

During exercise if there is limited access to the entire body (e.g. football or fire-fighters), cooling the hands, face and feet will help, and if possible, use a fan to increase evaporation from these surfaces. However, when heat stroke is suspected, these strategies are not nearly as effective as whole body methods; opt for immersion cooling.

So how do you know if someone is suffering from hyperthermia or heat stroke? A great resource is the Korey Stringer Institute, which lists many symptoms for heat stress such as fatigue, weakness, pale appearance, headache, nausea, vomiting, fainting, dizziness, and others. The heat stroke treatment they recommend, while geared toward athletes, is still useful for the rest of us. 

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Cold and calculating: what the two different types of ice do to sea levels

Posted on 20 July 2016 by Guest Author

Matt King, Professor, Surveying & Spatial Sciences, School of Land and Food, University of Tasmania; Ben Galton-Fenzi, Senior Scientist, and Will Hobbs, Physical Oceanographer, Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania

This article was originally published on The Conversation. Read the original article.

It was back in 250ʙⅽ when Archimedes reportedly stepped into his bathtub and had the world’s first Eureka moment – realising that putting himself in the water made its level rise.

More than two millennia later, the comments sections of news stories still routinely reveal confusion about how this same thing happens when polar ice melts and sea levels change.

This is in marked contrast to the confidence that scientists have in their collective understanding of what is happening to the ice sheets. Indeed, the 2014 Assessment Report of the Intergovernmental Panel on Climate Change reported “very high confidence” that the Greenland Ice Sheet was melting and raising sea levels, with “high confidence” of the same for the Antarctic Ice Sheet.

Despite this, commenters below the line on news stories frequently wonder how it can be true that Antarctica is melting and contributing to sea-level rise, when satellite observations show Antarctic ice expanding.

Unravelling the confusion depends on appreciating the difference between the two different types of ice, which we can broadly term “land ice” and “sea ice” – although as we shall see, there’s a little bit more to it than that. The two different types of ice have very different roles in Earth’s climate, and behave in crucially different ways.

Sea levels rise when ice resting on land, grounded ice, melts (often after forming icebergs). Floating sea ice that melts has a very important role in other areas of our climate system.

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Reshuffle: DECC folded into new department headed by Greg Clark

Posted on 19 July 2016 by Guest Author

This is a re-post from Carbon Brief by Sophie Yeo

Theresa May, the new prime minister, has axed the Department of Energy and Climate Change, by folding it into the Department for Business, Innovation & Skills and thereby creating a new ministry called the Department for Business, Energy and Industrial Strategy.

Greg Clark, who was the secretary of state for the Department for Communities and Local Government under David Cameron, was appointed head of the new department during a dramatic cabinet reshuffle on Thursday.

Reacting to his appointment, Clark said:

I am thrilled to have been appointed to lead this new department charged with delivering a comprehensive industrial strategy, leading government’s relationship with business, furthering our world-class science base, delivering affordable, clean energy and tackling climate change.

It is not Clark’s first brush with the climate change brief. Between 2008 and 2010, while the Conservatives were in opposition, he was shadow secretary for energy and climate change.

In this time, he made his views clear on climate change. Here are some quotes that might give us some idea of what to expect from him in the future.

2009: On climate science

Advances in climate science mean that we have an increasingly good idea of what the most likely outcome is for a particular level of carbon in the atmosphere – and, on current trends, this would be bad enough. Yet, we can’t overlook the fact that these represent midrange estimates. That might not matter if we could be certain that the actual outcomes won’t deviate very far from the central predictions; but, to use the statistical jargon, these are left-tailed, fat-tailed distributions – meaning that the worst that could happen is really very bad indeed.

2009: On extreme risks

Thanks to factors such as the release of methane from melting permafrost, there is a danger that higher temperatures could trigger a vicious circle of runaway global warming, with truly disastrous consequences. There are some risks, which are so extreme, so unpredictable, so global in their consequences, that they can’t be tolerated.
We’ve come to know these as ‘black swans’, a term made infamous by the credit crunch, where conventional risk management techniques came spectacularly unstuck. When faced with a black swan risk the only way to protect yourself is to reduce your exposure in the first place. In the case of climate change, that means ending our grand experiment with the planet’s atmosphere. The net costs of decarbonising the economy should therefore be regarded as an insurance policy – much as any sensible householder would pay to insure themselves against the remote, but real, risk of fire and flood. And not just the climate risks.The insurance principle doesn’t just apply to climate change.

2009: On climate sceptics

Some have asked can we continue to afford to fight climate change at a time like this? Shouldn’t we perhaps put it off until the economy gets moving again? It’s a good question… though one that is sometimes asked in bad faith by those who’d oppose action on climate change at anytime. That might be because they just don’t believe the mainstream scientific position on climate change or, in some cases, because it doesn’t suit their vested interests. Either way, the recession argument is, for them, just the latest in a series of delaying tactics.

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Déjà vu: as with tobacco, the climate wars are going to court

Posted on 18 July 2016 by dana1981, JohnMashey

Investigative journalism has uncovered a “web of denial” in which polluting industries pay “independent” groups to disseminate misinformation to the public and policymakers. The same groups and tactics were employed first by the tobacco industry, then fossil fuel companies. Big Tobacco has been to court and lost; now it’s Big Oil’s turn. Political leaders are choosing sides in this war.

Research by Inside Climate News revealed that Exxon did top notch climate science research in the late 1970s and early 1980s, which revealed the dangers its products posed via climate change. Soon thereafter, Exxon launched misinformation campaigns by funding “think tanks” and front groups to manufacture doubt about climate science and the expert consensus on human-caused global warming.

exxon knew vs did

What #ExxonKnew vs what #ExxonDid. Illustration: John Cook, SkepticalScience.com

Exxon wasn’t alone. Koch Industries, Peabody Energy, and other fossil companies have similarly funneled vast sums of money to these groups. Last week, Senate Democrats, including presidential candidate Bernie Sanders and vice presidential contenders Elizabeth Warren and Al Franken signed a Resolution expressing congressional disapproval of the fossil fuel industry’s misinformation campaign.19 Senate Democrats also took to the floor of the Senate to speak out against the web of denial, with repeated references to the tobacco/fossil connections.

 

Senator Elizabeth Warren speaking about the web of denial on the Senate floor.

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2016 SkS Weekly Digest #29

Posted on 17 July 2016 by John Hartz

SkS Highlights... Toon of the Week... Quote of the Week... He Said What?... SkS Spotlights... Coming Soon on SkS... Poster of the Week... SkS Week in Review... 97 Hours of Consensus...

SkS Highlights

Using the metric of number of comments garnered, the two most popular articles posted on SkS during the past week were:

Toon of the Week

 2016 Toon 29

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2016 SkS Weekly News Roundup #29

Posted on 16 July 2016 by John Hartz

A chronological listing of the news articles posted on the Skeptical Science Facebook page during the past week.

Sun July 10, 2016

  • Christiana Figueres launches UN secretary general bid by Ed King, Climate Home, July 7, 2016
  • Figueres win would mainstream climate change at UN by Nick Mabey, Climate Home, July 8, 2016
  • 'Shocking images' reveal death of 10,000 hectares of mangroves across Northern Australia by Kate Wild, ABC News, July 10, 2016
  • Nearly half a million leave home as storm left by super typhoon Nepartak hits China by Nathaniel Taplin, Reuters, July 9, 2016
  • The Carbon Brief Interview: Averil Macdonald by Simon Evans, Carbon Brief, July 5, 2016
  • How the World’s Most Fertile Soil Can Help Reverse Climate Change by David Suzuki, Ecowatch, July 6, 2016
  • Neocons linked to Tea Party paid for Andrea Leadsom’s flights to US by Jamie Doward, Observer/Guardian, July 9, 2016
  • Facing historically low levels, Lake Mead officials are fending off a water war. Here's how by William Yardley, Los Angeles Times, July 6, 2016
  • Read more...

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    Humans are greening the planet, but the implications are complicated

    Posted on 15 July 2016 by John Abraham

    The Earth’s climate is changing – in fact, it always changes. But in the current context of human influence, scientists try to decipher how much of the change is natural compared to human-induced.

    One clear way humans influence the Earth is through the biosystem. For instance, farming changes the biosystem. By removing natural growth and planting annual crops that are harvested, we change the system in a way that could in turn affect other parts of the Earth system. In addition, the use of nitrogen based fertilizers can increase growth rate and lead to a greening of areas that are subject to fertilization. 

    Another more indirect potential for humans to alter plant growth is through fertilization involving carbon dioxide. We know that humans have increased the amount of carbon dioxide in the atmosphere by approximately 40%. We also know that airborne carbon dioxide is a fertilizer for plants. So the obvious question is, “do our carbon emissions affect plant growth?”.

    A new study, just out in Nature Climate Change, helps answer that question. This study focused on land areas in the northern hemisphere that were outside the tropical region. They obtained information from satellites to measure the greening of these lands areas to determine whether there was any significant change. The find that yes, in fact there is. Over approximately 30-year durations, this area has indeed gotten greener.

    So, the next question is, what is causing the greening? To answer this question, the authors used computer simulations and ran them with and without human influences. When we say “human influences” we can mean many things, such as increase or decrease of farming, use of fertilizers, and airborne increase of carbon dioxide, just to name a few. The authors found that the only way the simulations matched the observations is when these human influences were included. That is, solely natural variations cannot be the cause. Not only that, but the match worked best when airborne carbon dioxide had a major role.

    model

    The spatial distribution of the linear trends in the growing season (April–October) leaf area index during the period 1982–2011 in the mean of satellite observations (upper figure), Earth system model (ESM) simulations with natural forcings alone (lower left figure), and ESM simulations with anthropogenic and natural forcings (lower right figure). Illustration: Oak Ridge National Laboratory

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    Will the health dangers of climate change get people to care? The science says: maybe

    Posted on 14 July 2016 by Guest Author

    Matthew Nisbet, Associate Professor of Communication, Northeastern University

    This article was originally published on The Conversation. Read the original article.

    Climate change is a major public health threat, already making existing problems like asthma, exposure to extreme heat, food poisoning, and infectious disease more severe, and posing new risks from climate change-related disasters, including death or injury.

    Those were the alarming conclusions of a new scientific assessment report released by the Obama administration this week, drawing on input from eight federal agencies and more than 100 relevant experts.

    “As far as history is concerned this is a new kind of threat that we are facing,“ said U.S. Surgeon General Vivek Murthy at a White House event. Pregnant women, children, low-income people and communities of color are among the most at risk.

    Despite ever more urgent warnings of scientists, Americans still tend to view climate change as a scientific or environmental issue, but not as a problem that currently affects them personally, or one that connects to issues that they already perceive as important.

    Yet research suggests that as federal agencies, experts, and societal leaders increasingly focus on the public health risks of climate change, this reframing may be able to overcome longstanding public indifference on the issue. The new communication strategy, however, faces several hurdles and uncertainties.

    Putting a public health focus to the test

    In a series of studies that I conducted with several colleagues in 2010 and 2011, we examined how Americans respond to information about climate change when the issue is reframed as a public health problem.

    In line with the findings of the recent Obama administration report, the messages we tested with Americans stressed scientific findings that link climate change to an increase in the incidence of infectious diseases, asthma, allergies, heat stroke and other health problems – risks that particularly impact children, the elderly and the poor.

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    Global warming implicated in dinosaur extinction

    Posted on 13 July 2016 by howardlee

    In a paper published on Tuesday in the journal Nature Communications, scientists from the University of Michigan and the University of Florida show that there were big jumps in climate warming when the dinosaurs went extinct at the end of the Cretaceous. This brings the end-Cretaceous mass extinction in line with the other mass extinction events, which occurred at times of abrupt and sometimes extreme climate change (including the end-Permian, the end-Triassic, the Toarcian, and others).

    By employing a relatively new ancient-temperature-measuring technique called “carbonate clumped isotope paleothermometry,” scientists have uncovered an 8ºC jump in seawater temperatures that unfolded rapidly, at the same time as massive CO2 emissions from the Indian Deccan Traps eruptions (“rapidly” here means anything less than about 30,000 years, possibly centuries; such are the limits of time resolution). They also found a second, smaller spike in warming about 150,000 years later, at around the same time as the asteroid impact at Chicxulub in Mexico.

    mollusk

    A mollusk that lived in Antarctica in the final years of the Cretaceous, showing the holes made by scientists extracting material to measure ancient sea temperatures. Photograph: Sierra V. Petersen

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    Why Paris climate pledges need to overdeliver to keep warming to 2C

    Posted on 12 July 2016 by Guest Author

    This is a re-post from Carbon Brief by Dr Joeri Rogelj, a research scholar at the International Institute for Applied Systems Analysis (IIASA) in Austria. Rogelj was recently awarded the inaugural Piers Sellers Prize for world leading contribution to solution-focused climate research.

    Last year’s Paris Agreement is considered a major global step in addressing the threat of climate change.

    It was a diplomatic victory to bring 195 governments together to agree a goal to limit global average temperature increase to “well below 2C” relative to pre-industrial levels, and to “pursue efforts” to limit it to 1.5C.

    It was a similar tour de force that 186 parties submitted “intended nationally determined contribution” (INDCs) in the run up to Paris. INDCs set out each country’s contribution to cutting greenhouse gas emissions in order to meet the collective global temperature goal. The INDC process succeeded in overcoming decades of hesitation across the international community.

    Moreover, every five years, these contributions are to be updated or renewed, steadily increasing in ambition.

    But accompanying this success came a set of puzzling questions: what do the INDCs add up to in terms of global emissions reductions? Are they sufficient to keep warming to well below 2C? If not, what temperature increase are we heading for? What about 1.5C? And, are the INDCs at least a step in the right direction?

    An added complication is that INDCs don’t all follow the same approach. Some countries’ emissions pledges are conditional on receiving funding, for example, while others depend on the growth of their economy. This is why various studies (pdf) addressing these questions have often come up with different answers.

    Our new paper, just published in Nature, provides some clarity on this issue by carrying out a “meta-analysis” to see what conclusions we can draw from ten of these studies.

    And to cut a long story short, the INDCs alone do not keep warming to well below 2C.

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    We just broke the record for hottest year, nine straight times

    Posted on 11 July 2016 by dana1981

    2014 and 2015 each set the record for hottest calendar year since we began measuring surface temperatures over 150 years ago, and 2016 is almost certain to break the record once again. It will be without precedent: the first time that we’ve seen three consecutive record-breaking hot years.

    But it’s just happenstance that the calendar year begins in January, and so it’s also informative to compare all yearlong periods. In doing so, it becomes clear that we’re living in astonishingly hot times.

    June 2015 through May 2016 was the hottest 12-month period on record. That was also true of May 2015 through April 2016, and the 12 months ending in March 2016. In fact, it’s true for every 12 months going all the way back to the period ending in September 2015, according to global surface temperature data compiled by Kevin Cowtan and Robert Way. We just set the record for hottest year in each of the past 9 months.

    CW13 running

    Running 12-month average global surface temperature using data compiled by Kevin Cowtan and Robert Way. Illustration: Dana Nuccitelli

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    10 comments


    2016 SkS Weekly Digest #28

    Posted on 10 July 2016 by John Hartz

    SkS Highlights... Toon of the Week... Quote of the Week... They Said What?... Graphic of the Week... Coming Soon on SkS... Poster of the Week... SkS Week in Review... 97 Hours of Consensus...

    SkS Highlights

    The SkS Facebook page has reached a new milestone of 175,000 Likes. Try it, you'll like it. 

    Toon of the Week

    2016 Toon 28 

    Hat tip to I Heart Climate Scientists

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    2016 SkS Weekly News Roundup #28

    Posted on 9 July 2016 by John Hartz

    A chronological listing of the news articles posted on the Skeptical Science Facebook page during the past week.

    Sun July 3, 2016

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    6 comments


    Aerosol emissions key to the surface warming ‘slowdown’, study says

    Posted on 8 July 2016 by Guest Author

    This is a re-post from Carbon Brief by Robert McSweeney

    In the early 2000s, the rate of warming at the Earth’s surface was slower than scientists expected, despite the continued accumulation of CO2 in the atmosphere.

    Recent research has shown that natural fluctuations in the Pacific Ocean played an important role in this surface warming “slowdown”.

    But a new paper, published in Nature Climate Change, suggests these variations in the Pacific Ocean were actually triggered by changing aerosol emissions from human activity – particularly by increases in China’s burning of fossil fuels.

    The findings suggest that the slowdown in surface warming could have been predicted, the lead author tells Carbon Brief, and that future cuts to aerosol emissions could prompt rapid warming in the coming years.

    Cooling effect

    In its latest report, the IPCC calculated (pdf) that global surface temperatures between 1998 and 2012 rose by 0.05C per decade. Accounting for uncertainty, this is 30-50% slower than the 0.12C per decade increase over the longer period of 1951-2012.

    This apparent slowdown in surface warming has prompted a flurry of research papers as scientists seek to identify its cause.

     

    The overall conclusion from published research suggests there is no single reason for the slowdown, but rather a series of contributing factors. One of the principal causes is thought to be fluctuations in the Pacific Ocean.

    These fluctuations are usually known as the Pacific Decadal Oscillation (PDO). The PDO has two opposite phases: positive (also known as the “warm” phase) and negative (“cool”), which each affect global weather in different ways.

    The phases of the PDO also affect the strength of the trade winds that blow east-to-west across the tropical Pacific Ocean. These winds are driven by warm air rising along the equator and the rotation of the Earth.

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    Climate scientists are under attack from frivolous lawsuits

    Posted on 7 July 2016 by Guest Author

    Lauren Kurtz is the Executive Director of the Climate Science Legal Defense Fund(CSLDF), a non-profit that defends scientists against legal attack. CSLDF was founded to fund Dr. Mann’s defense, represented Dr. Maibach, and filed amicus briefs in support of the University of Arizona. Help protect the scientific endeavor by donating to CSLDF, where a trustee is currently matching all donations up to $50,000.

    On June 14th, an Arizona court ruled that thousands of emails from two prominent climate scientists must be turned over to the Energy & Environment Legal Institute (E&E), a group that disputes the 97% expert consensus on human-caused climate change and argues against action to confront it. E&E and its attorneys are funded by Peabody CoalArch Coal, and Alpha Natural Resources, coal corporations with billions of dollars in revenue. 

    Formerly named the American Tradition Institute, E&E has been described as “filing nuisance suits to disrupt important academic research.”

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    1 comments


    Trump's energy plan poses climate threat to U.S. economy

    Posted on 6 July 2016 by Guest Author

    by The ConversationRobert Kopp, Rutgers University

    Last December in Paris, the nations of the world agreed to an ambitious goal for greenhouse gas emissions: to bring net emissions to zero in the second half of this century. Their objective: to limit global warming to 1.5 to 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) above preindustrial temperatures, or equivalently about 0.5 to 1.0°C (0.9 to 1.8°F) above the current global average temperature.

    The Paris Agreement set up a process by which countries commit to emissions targets and then, every five years, report on their progress and make increasingly stringent new commitments. Current national commitments, which lay out targets for the 2025-2030 time frame, aren’t enough to get us to the long-term goal. But the current commitments and the new process constitute a major step toward breaking the dangerous fossil fuel addiction of the last two centuries.

    Market forces and public policy in the U.S. and around the world are already helping push the world away from carbon-intensive fuels and toward renewable energy. U.S. carbon dioxide emissions peaked in 2007, and it’s possible that Chinese emissions peaked in 2014. This market-led, policy-accelerated shift is making reduction goals more attainable than they seemed a decade ago.

    Donald Trump’s “America First” energy plan, outlined in May and focused on expanding fossil-fuel production, would reverse these advances. Trump has promised to “cancel” the Paris climate agreement and pledged to reopen coal mines – a pledge which, given the unfavorable economics of coal mining, he could fulfill only through a massive expansion of corporate welfare for coal companies.

    Backing out of the Paris Agreement would undermine U.S. leadership and stall greenhouse gas reduction efforts around the world. And expanding production of coal could return us to the pathway of rapidly rising emissions that characterized the 2000s.

    The climate consequences of such a great leap backwards would be severe. Far from placing America first, they would threaten the health of Americans and of the American economy – not to mention people and economies throughout the world.

    Different pathways

    Two years ago, I co-led an analysis of several key climate-change-related risks facing the United States. Our team used state-of-the-art climate and economic models to assess multiple scenarios for the current century.

    These scenarios, developed by the international climate modeling community, include a high-emissions future with expanded fossil fuel use and a low-emissions future in which, consistent with the aspirations of the Paris agreement, emissions go to zero in the second half of this century. Comparing the highest and lowest scenarios – let’s call them the Trump Trajectory and the Paris Path – provides a sense of the risks Donald Trump’s energy policy poses to our country and the planet.

    Using the high scenario as a proxy for Trump’s policy, what changes could we expect?

    Expected number of days in a typical year with highs above 95°F under the Trump Trajectory. Rasmussen et al., 2016, Author provided

    Carbon dioxide concentrations in Earth’s atmosphere will average about 404 parts per million (ppm) this year. While the Paris Path would keep them from rising above 450 ppm, the Trump Trajectory would elevate them over 550 ppm in the 2050s and – if policies consistent with rapid expansion of fossil fuel production were maintained – over 900 ppm in the 2090s.

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    New research: climate may be more sensitive and situation more dire

    Posted on 5 July 2016 by dana1981

    Scientists use a variety of approaches to estimate the Earth’s climate sensitivity – how much the planet will warm as a result of humans increasing greenhouse effect. For decades, the different methods were all in good general agreement that if we double the amount of carbon dioxide in the atmosphere, Earth’s surface temperatures will immediately warm by about 1–3°C (this is known as the ‘transient climate response’). Because it would take decades to centuries for the Earth to reach a new energy balance, climate scientists have estimated an eventual 2–4.5°C warming from doubled atmospheric carbon (this is ‘equilibrium climate sensitivity’).

    However, a 2013 paper led by Alexander Otto disrupted the agreement between the various different approaches. Using a combination of recent climate measurements and a relatively simple climate model, the ‘energy budget’ approach used in Otto’s study yielded a best estimate for the immediate (transient) warming of 1.3°C and equilibrium warming of 2.0°C; within the agreed range, but less than climate model best estimates of 1.8°C and 3.2°C, respectively.

    This new energy budget approach, which was replicated by several subsequent studies, seemed to indicate the Earth’s climate is a bit less sensitive to carbon pollution than previously thought. As a result, the IPCC adjusted its estimated range for equilibrium climate sensitivity from 2–4.5°C in its 2007 report to 1.5–4.5°C in its 2014 report. This suggested perhaps a slightly less dire climate situation.

    New finding: disagreement due to apples-to-oranges comparison

    Later in 2013, Kevin Cowtan and Robert Way published a paper finding that climate scientists had been underestimating global surface warming, largely because of a lack of measurements in the rapidly-warming Arctic. Additionally, while climate models simulate surface air temperatures (the temperature of the air a few meters above the Earth’s surface), over the oceans, climate scientists measure sea surface temperatures. It turns out that the water surface isn’t warming quite as fast as the air above it. Thus looking at modeled surface air temperatures versus measured global land-ocean surface temperatures is an apples-to-oranges comparison.

    A new study in Nature Climate Change led by Mark Richardson in collaboration with Kevin Cowtan, Ed Hawkins, and Martin Stolpe accounts for these differences to make an apples-to-apples comparison. They find that the use of sea surface temperatures biases the Otto result low by about 9%, and the lack of Arctic observations by another 15%. When observations are adjusted to estimate surface air temperatures (red bars in the figure below), or when models are adjusted to estimate land-ocean surface temperatures (blue bars), the estimated transient climate response from climate models and the Otto approach are in close agreement.

    apples to apples

    Like-with-like comparisons of transient climate response estimates between models and observations. In the upper two bars, the observed estimates are adjusted to match the method used for the models. In the lower three bars the model outputs are treated in the same way as the observations. Illustration: Richardson et al. (2016); Nature Climate Change.

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    1 comments


    2016 SkS Weekly Digest #27

    Posted on 3 July 2016 by John Hartz

    SkS Highlights... Toon of the Week... Quote of the Week... Internet Buzz... Graphic of the Week... SkS Spotlights... Coming Soon on SkS... Poster of the Week... SkS Week in Review... 97 Hours of Consensus...

    SkS Highlights

    The inter-generational theft of Brexit and climate change by Dana Nuccitelli (Climate Consensus - the 97%, Guardian) attacted the highest number of comments of the articles posted on SkS during the past week. 

    Today's edition of the Weekly Digest contains two new sections -- Internet Buzz by David Kirtley and Graphic of the Week. Be sure to check them out.

    Toon of the Week

    2016 Toon 27

    Hat tip to I Heart Climate Scientists

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