Global Warming and the Influence of the Sun

From Real Climate

Is the sun (sun spots) responsible for global warming?

Will There Be Another Ice Age?

By Kara Rogers, Science Friday, April 10, 2013

If Earth's past climates tell us anything, it’s that ice will return. Over the last 2.6 million years, the planet has experienced a series of glacial periods separated by thaws, or interglacials. The next big chill could hit within two millennia—that is, if it weren’t for soaring levels of atmospheric carbon dioxide, driven by humans.

“Climate modelers have been warning for many years now that the net impact of human activities would prolong the current interglacial,” says Chronis Tzedakis, a climate scientist at University College London.

A medley of forces influences the glacial-interglacial cycle, including the amount of solar radiation reaching the Earth, which is controlled mainly by Earth's orbital shape and axial tilt, the composition of gasses and aerosols and extent of cloud cover in the atmosphere, and the reflectivity of Earth’s surface (for example, the extent of ice and vegetation cover at high latitudes). A reduction in incoming summer solar radiation would be the primary trigger for glaciation, but atmospheric CO2 concentrations—the primary driver of climate change—must be relatively low, too.

How low is “relatively low”? Tzedakis and colleagues compared ice and marine records from previous interglacials and found that, given the current small decrease in summer solar radiation, CO2 concentrations would have to fall to around 240 ppm for the next glacial period to take place.

Since the Industrial Revolution, however, atmospheric CO2 levels have been trending higher and higher. They reached an estimated 395.09 ppm globally in January 2013. So, if business proceeds as usual, with carbon release being driven primarily by fossil-fuel burning, we likely have a long thaw ahead of us. Modeling work by geophysical scientist David Archer has shown, for instance, that burning all potential fossil carbon on Earth—5,000 gigatons—would be enough to delay the next glaciation by 500,000 years.

That kind of hold-up would be a major deviation from the glacial-interglacial cycle that has played out over the last couple million years, in which glacial periods lasted about 80,000–90,000 years and interglacials about 10,000–20,000 years. (The current interglacial began about 11,500 years ago.)

The real question, then, might have more to do with the next “age,” generally, that we face, rather than the next ice age. Some scientists consider the current era to be defined by human influence, what Dutch chemist Paul J. Crutzen dubbed the Anthropocene Epoch, which has its origins in the Industrial Age.

Regardless of what comes next, it’s probably safe to say that we can’t expect a resurgence of woolly mammoths any time soon. Unless we clone them.

The Hiatus in Global Warming Has Deniers in Paroxyms of Joy; It is However, Unwarranted

From The Economist, March 8, 2014

BETWEEN 1998 and 2013, the Earth’s surface temperature rose at a rate of 0.04°C a decade, far slower than the 0.18°C increase in the 1990s. Meanwhile, emissions of carbon dioxide (which would be expected to push temperatures up) rose uninterruptedly. This pause in warming has raised doubts in the public mind about climate change. A few sceptics say flatly that global warming has stopped. Others argue that scientists’ understanding of the climate is so flawed that their judgments about it cannot be accepted with any confidence. A convincing explanation of the pause therefore matters both to a proper understanding of the climate and to the credibility of climate science—and papers published over the past few weeks do their best to provide one. Indeed, they do almost too good a job. If all were correct, the pause would now be explained twice over.

This is the opposite of what happened at first. As evidence piled up that temperatures were not rising much, some scientists dismissed it as a blip. The temperature, they pointed out, had fallen for much longer periods twice in the past century or so, in 1880-1910 and again in 1945-75 (see chart), even though the general trend was up. Variability is part of the climate system and a 15-year hiatus, they suggested, was not worth getting excited about.

An alternative way of looking at the pause’s significance was to say that there had been a slowdown but not a big one. Most records, including one of the best known (kept by Britain’s Meteorological Office), do not include measurements from the Arctic, which has been warming faster than anywhere else in the world. Using satellite data to fill in the missing Arctic numbers, Kevin Cowtan of the University of York, in Britain, and Robert Way of the University of Ottawa, in Canada, put the overall rate of global warming at 0.12°C a decade between 1998 and 2012—not far from the 1990s rate. A study by NASA puts the “Arctic effect” over the same period somewhat lower, at 0.07°C a decade, but that is still not negligible.

It is also worth remembering that average warming is not the only measure of climate change. According to a study just published by Sonia Seneviratne of the Institute for Atmospheric and Climate Science, in Zurich, the number of hot days, the number of extremely hot days and the length of warm periods all increased during the pause (1998-2012). A more stable average temperature hides wider extremes.

Still, attempts to explain away that stable average have not been convincing, partly because of the conflict between flat temperatures and rising CO2 emissions, and partly because observed temperatures are now falling outside the range climate models predict. The models embody the state of climate knowledge. If they are wrong, the knowledge is probably faulty, too. Hence attempts to explain the pause.

In September 2013 the Intergovernmental Panel on Climate Change did so in terms of fluctuating solar output, atmospheric pollution and volcanoes. All three, it thought, were unusually influential.
The sun’s power output fluctuates slightly over a cycle that lasts about 11 years. The current cycle seems to have gone on longer than normal and may have started from a lower base, so for the past decade less heat has been reaching Earth than usual. Pollution throws aerosols (particles such as soot, and suspended droplets of things like sulphuric acid) into the air, where they reflect sunlight back into space. The more there are, the greater their cooling effect—and pollution from Chinese coal-fired power plants, in particular, has been rising. Volcanoes do the same thing, so increased volcanic activity tends to reduce temperatures.

Gavin Schmidt and two colleagues at NASA’s Goddard Institute quantify the effects of these trends in Nature Geoscience. They argue that climate models underplay the delayed and subdued solar cycle. They think the models do not fully account for the effects of pollution (specifically, nitrate pollution and indirect effects like interactions between aerosols and clouds). And they claim that the impact of volcanic activity since 2000 has been greater than previously thought. Adjusting for all this, they find that the difference between actual temperature readings and computer-generated ones largely disappears. The implication is that the solar cycle and aerosols explain much of the pause.

There is, however, another type of explanation. Much of the incoming heat is absorbed by oceans, especially the largest, the Pacific. Several new studies link the pause with changes in the Pacific and in the trade winds that influence the circulation of water within it.

Trade winds blow east-west at tropical latitudes. In so doing they push warm surface water towards Asia and draw cooler, deep water to the surface in the central and eastern Pacific, which chills the atmosphere. Water movement at the surface also speeds up a giant churn in the ocean. This pulls some warm water downwards, sequestering heat at greater depth. In a study published in Nature in 2013, Yu Kosaka and Shang-Ping Xie of the Scripps Institution of Oceanography, in San Diego, argued that much of the difference between climate models and actual temperatures could be accounted for by cooling in the eastern Pacific.

Every few years, as Dr Kosaka and Dr Xie observe, the trade winds slacken and the warm water in the western Pacific sloshes back to replace the cool surface layer of the central and eastern parts of the ocean. This weather pattern is called El Niño and it warms the whole atmosphere. There was an exceptionally strong Niño in 1997-98, an unusually hot year. The opposite pattern, with cooler temperatures and stronger trade winds, is called La Niña. The 1997-98 Niño was followed by a series of Niñas, explaining part of the pause.

Switches between El Niño and La Niña are frequent. But there is also a long-term cycle called the Pacific Decadal Oscillation (PDO), which switches from a warm (or positive) phase to a cool (negative) one every 20 or 30 years. The positive phase encourages more frequent, powerful Niños. According to Kevin Trenberth and John Fasullo of America’s National Centre for Atmospheric Research, the PDO was positive in 1976-98—a period of rising temperatures—and negative in 1943-76 and since 2000, producing a series of cooling Niñas.

But that is not the end of it. Laid on top of these cyclical patterns is what looks like a one-off increase in the strength of trade winds during the past 20 years. According to a study in Nature Climate Change, by Matthew England of the University of New South Wales and others, record trade winds have produced a sort of super-Niña. On average, sea levels have risen by about 3mm a year in the past 30 years. But those in the eastern Pacific have barely budged, whereas those near the Philippines have risen by 20cm since the late 1990s. A wall of warm water, in other words, is being held in place by powerful winds, with cool water rising behind it. According to Dr England, the effect of the trade winds explains most of the temperature pause.

If so, the pause has gone from being not explained to explained twice over—once by aerosols and the solar cycle, and again by ocean winds and currents. These two accounts are not contradictory. The processes at work are understood, but their relative contributions are not.

Nor is the answer to what is, from the human point of view, the biggest question of all, namely what these explanations imply about how long the pause might continue. On the face of it, if some heat is being sucked into the deep ocean, the process could simply carry on: the ocean has a huge capacity to absorb heat as long as the pump sending it to the bottom remains in working order. But that is not all there is to it. Gravity wants the western-Pacific water wall to slosh back; it is held in place only by exceptionally strong trade winds. If those winds slacken, temperatures will start to rise again.

The solar cycle is already turning. And aerosol cooling is likely to be reined in by China’s anti-pollution laws. Most of the circumstances that have put the planet’s temperature rise on “pause” look temporary. Like the Terminator, global warming will be back.

Mount Doom Erupts!!

Tongariro National Park, in New Zealand, has three active volcanoes. It was the backdrop for many scenes in "The Lord of the Rings" movies. "Mount Doom" was shown spewing red hot lava and black smoke into a lowering sky. Today, a real volcanic eruption is happening there.

The eruption of Mount Tongariro, in Tongariro National Park, its second in less than four months, sent a dark ash plume about 1.9 miles into the sky. Authorities issued a no-fly alert above the mountain located in the sparsely populated area of central North Island.

If you’re worried about the Tongariro eruption adding to global warming, don’t worry -- volcanic eruptions can actually cool the earth, as none other than Benjamin Franklin noted in 1784. Volcanic eruptions create atmospheric haze, which decreases the amount of sunlight reaching the earth's surface and results in some cooling; the amount of the cooling depends on a number of factors, including the size of the eruption. Volcanoes can spew CO2 into the atmosphere, but the most unfortunate byproduct of their eruptions is Sulfur Dioxide SO2, which as it mixes with water vapor in the atmosphere, produces acid rain.

Volcanic eruptions in Iceland caused the cooling noted by Franklin in 1784, and Iceland’s Laki fissure system threw vast quantities of sulfur dioxide (SO₂), hydrogen chloride (HCl), and hydrogen fluoride gases (HF) high into the atmosphere. The gases combined with water in the atmosphere to produce acid rain, destroying crops and killing livestock. The effects were most severe in Iceland; ultimately, more than 75 percent of Iceland’s livestock and 25 percent of its human population died from famine or the toxic impact of the Laki eruption clouds. The effects of the Laki eruptions were felt far beyond Iceland, as well. A 2008 Scientific American article provides details on the effects of volcanoes on climate.

Volcanic eruptions have been implicated in the so-called “great dying” that occurred 65 million years ago. The catastrophe that resulted in the extinction of the dinosaurs, among other things, coincided with one of Earth's largest continental flood basalt provinces, the Siberian Traps. In other words, a gigantic volcanic eruption launched enormous amounts of gases into the atmosphere, compromising global ocean chemistry, causing climate change and, possibly, the destruction of the ozone layer, which would explain the land extinction.

Although volcanic eruptions do produce CO2, the amount created is nothing compared to what humans are producing each year, which is about 10,000 times the amount created by volcanoes.

Greenhouse Gases Rise to Record Levels in Atmosphere, WMO Says

By Alex Morales on November 20, 2012

Concentrations in the atmosphere of the three main gases blamed for global warming all rose in 2011 to their highest since records began, the United Nations said.

Carbon dioxide, responsible for about 80 percent of the global warming effect of greenhouse gases, gained 0.51 percent to 390.9 parts per million molecules of air, the UN’s World Meteorological Organization said today in an e-mailed bulletin. The methane concentration increased 0.28 percent and the nitrous oxide level rose 0.31 percent.

Rising concentrations of the three gases in the Earth’s atmosphere threaten to render impossible the UN’s goal of containing the temperature increase to below 2 degrees Celsius of warming since industrialization, the International Energy Agency said earlier this month.

“These billions of tonnes of additional carbon dioxide in our atmosphere will remain there for centuries, causing our planet to warm further and impacting on all aspects of life on Earth,” WMO Secretary-General Michel Jarraud said in the statement. “Future emissions will only compound the situation.”

UN climate treaty envoys gather in Doha next week for two weeks of talks to extend targets under the current emissions- limiting deal, the Kyoto Protocol, and to lay the groundwork for a new pact in 2015 that will take effect from 2020.

The methane concentration in 2011 was 1,813 parts per billion molecules of air, according to the WMO bulletin. The nitrous oxide concentration was 324.2 parts per billion.

A Bill to Prohibit Action on Reducing GHG Emissions

It seemed to surprise a lot of people when Mayor Michael R. Bloomberg endorsed Barack Obama for president in the final weeks of the 2012 Presidential Campaign. Bloomberg said that Hurricane Sandy had reshaped his thinking about the campaign. Although he wasn’t entirely enthusiastic about the incumbent president’s record on climate change, he felt that Obama was far more likely to take on the issue in his second term than Mitt Romney would in his first, or ever, for that matter. 

“Our climate is changing,” Bloomberg wrote. “And while the increase in extreme weather we have experienced in New York City and around the world may or may not be the result of it, the risk that it may be — given the devastation it is wreaking — should be enough to compel all elected leaders to take immediate action.”

Last summer, Bloomberg voiced his opposition to big coal. "If we are going to get serious about reducing our carbon footprint in the United States, we have to get serious about coal, " Bloomberg said. "Ending coal power production is the right thing to do, because while it may seem to be an inexpensive energy source the impact on our environment and the impact on public health is significant.  Coal is a self-inflicted public health risk, polluting the air we breathe, adding mercury to the water we drink and the leading cause of climate disruption.”

As evidence that he is serious, Bloomberg announced that his philanthropic foundation was giving $50 million over the next four years to help the Sierra Club expand it's "Beyond Coal" campaign. The money will allow the Sierra Club to expand its anti-coal campaign from 15 states to 45.  Michael Brune, Executive Director of the Sierra Club, said,”Our goal is to use this money to retire one-third of the coal plants in operation America today."

Alas, during the second presidential debate, Romney and Obama argued over who was the biggest supporter of coal. Yikes! As I’ve written previously, “No one following climate change developments could take any joy from the exchange, especially those fearing the earth is already experiencing what would be its sixth mass extinction.”

So, have Republicans changed their minds about the need for action on climate change after Sandy took a big bite out of the Big Apple and Jersey Shores? Hardly. Congressional Republicans have pushed a bill, S.1956, that would, “prohibit operators of civil aircraft of the United States from participating in the European Union's [greenhouse gas - GHG] emissions trading scheme.” The bill’s sponsor is South Dakota Republican, John Thune, whose state is one of the few in the nation that allows the statewide use of conventional motor gasoline. Unfortunately, this bill seems to have the support of the Administration, which objects to the EU’s “unilateral” action to combat climate change.

If the rest of the world expects the United States of America to take the lead on a global initiative to reduce greenhouse gas emissions, they have sorely underestimated the influence the fossil fuel industry has on US energy policy. In the meantime, expect the US to oppose anything that smacks of "unilateralism" on climate change.

Too bad. For all of us.

Obama faces first post-election climate test

By Glenn Hurowitz

Grist guest contributor

President Obama will start to determine his second-term approach to climate change today as the House of Representatives sends final legislation (see note at end of post) to his desk that empowers him to bar U.S. airlines from complying with Europe’s climate law. If he signs the bill, Obama will not only be failing to take sufficient action to address climate change, but actively going out of his way to stop another country from doing so – a pretty extreme act at the worst possible time.

The controversy: the European Union has finally ended  airlines’ exemption from European pollution rules, and has applied its law equally to domestic and international flights that take off or land in Europe.  The policy is a big deal: it cuts pollution by an amount equivalent to taking 30 million cars off the road by 2020 – and does it at a cost of about three dollars per trans-Atlantic flight, less than the cost of a bag of absurdly expensive potato chips peddled to passengers during the flight. And far less than the $16.70 fee that the United States levies for every international flight that takes off and lands here.

If the President signs the Thune bill, US taxpayers could be on the hook for paying the up to $22 billion in fines airlines are expected to accrue for their law-breaking. It’s as if a American business tycoon went to Paris, stole the Mona Lisa, and then got US taxpayers to pay the Louvre billions of dollars in compensation.

The Thune bill is pretty unprecedented – and if President Obama signs it, the United States will suddenly be in the business of pretending to decide the legality of Europe’s regulations – which I’m pretty sure is not in the Constitution.

To try and make President Obama’s decision easier, the European Union on Monday agreed to delay implementation of its law for foreign airlines by six months to give the International Civil Aviation Organization time to work out a global deal to cut airline pollution. Though ICAO has languished unproductively for 15 years in pursuit of such an aim—stymied by the airlines’ lobby -Europe’s climate law has breathed new life into the negotiations, generating some very cautious optimism that a global agreement may be on the horizon.  The Obama administration says it backs such an agreement, but under pressure from United Airlines and others, refuses to support anything concrete that would actually reduce pollution.

In other words, President Obama would be giving New Yorkers hungry for climate action a big old extremely soggy blanket. It’s like when Gerald Ford refused to help New York City during its hour of greatest need, the 1970′s fiscal crisis – and New York produced one of the great headlines of all time, “Ford to City: Drop Dead.” (Ford subsequently blamed the headline for his 1976 election defeat).  Now, New York is in an hour of perhaps even greater need, and President Obama is threatening to abandon New Yorkers and all Americans to their fates when it comes to the rising seas swamping our neighborhoods.

As a native New Yorker, it’s hard to wrap my head around the idea that the President would consider being so callous. My in-laws on Long Island have been picking dead fish out of their closets for the last two weeks, lost their cars to the storm surge, and have months of recovery ahead of them – all due to a storm that at a minimum was made worse by rising sea levels. For President Obama to come in and tell them and other Sandy victims that he cares more about the airline lobby than their well-being and the global climate would be an epic disappointment, and a sweeping failure for his administration and legacy.

Note: On Tuesday, November 13, 2012, the House is scheduled to consider S. 1956, a bill to prohibit operators of civil aircraft of the United States from participating in the European Union’s emissions trading scheme (ETS), under a suspension of the rules requiring a two-thirds majority vote for passage.  The bill was introduced by Sen. John Thune (R-SD) on December 7, 2011 and referred to the Committee on Commerce, Science, and Transportation. S. 1956 passed the Senate with an amendment by Unanimous Consent on September 22, 2012. The bill was sent to the House and referred to the House Committee on Transportation and Infrastructure on September 25, 2012.

Going Extinct

In what seemed to me a bizarre encounter in the second presidential debate, the incumbent president and his challenger argued over which of the contenders for leader of the free world was more supportive of coal -- America's dirtiest energy source, and the country's leading source of pollution. No one following climate change developments could take any joy from the exchange, especially those fearing the earth is already experiencing what would be its sixth mass extinction.

Human activities are causing the earth to warm. There are no national or major scientific institutions anywhere in the world that dispute the theory of anthropogenic global warming (AGW). Not one. And we are already seeing the effects: longer, more intense heat waves, extreme drought, increased incidence of wildfires and longer fire seasons, loss of Arctic sea ice, and ocean acidification, among other things.

It will get worse, perhaps catastrophically so. Why? Because: (1) carbon dioxide (CO2), the primary driver of human-caused warming, takes centuries to dissipate in the atmosphere and global CO2 emissions continue to rise; and (2) many of the drivers of global warming produce positive feedbacks -- they are self-reinforcing -- and thus amplify the effects of global warming.

An example of positive feedback is the melting of Arctic sea ice. When sea ice melts, open water takes its place and being less reflective than ice, absorbs more solar radiation. This causes more warming, which in turn causes more melting.

To those who admit to anthropogenic global warming, but are content to wait it out, I suggest that their complacency, as well as being shamefully self-centered, may well be misplaced. Why? Because there’s the potential for a catastrophic climate destabilization.

Destabilization is an abrupt change in climate that would trigger dramatically shifting weather patterns, producing coastal flooding and torrential rains in some regions, and extreme drought in others, as well as an increasing incidence of hurricanes and tornadoes. These weather phenomena could occur in areas not normally accustomed to such events, such as the tornadoes that touched down in New York City in September of 2012, and super storm Sandy, that devastated the East Coast in October of that same year. In short, destabilization would lead to climate hell today, not in 2050.

Aftermath of Super Storm Sandy, Queens NY, 10/30/2012

Is this science fiction? Not at all. Paleoclimate records indicate that climate changes of this size and speed have occurred many times in the past. Furthermore, studies of the earth’s past five mass extinctions, including the one that wiped out the dinosaurs 65 million years ago (mya), have shown that a buildup of atmospheric carbon dioxide is a concomitant, if not the driving factor, in extinction events. The most devastating extinction in earth’s history, the Permian mass extinction, which occurred 252 mya, has been linked to a massive release of CO2 and/or methane.

At over 390 ppm, the amount of carbon dioxide in the atmosphere currently is unprecedented, at least in the last 400,000 years. At the same time, we are seeing the release of methane (a greenhouse gas 60 times more powerful than CO2) from thawing permafrost, as well as from the Arctic sea bed, and from unstable water bound deposits all over the world. The release of methane is a self-reinforcing process. A runaway methane release will very likely trigger abrupt climate change, and bring earth’s sixth mass extinction event to its apogee, and the destruction of most life on earth.

If we can go by the record of past mass extinctions, the earth will, over a few million years recover from this human-caused extinction event, but earth’s newly evolving tree of life will develop in whatever way the environment dictates. The chances the tree will include a homo sapiens limb is slim to none, which is probably for the best. We had our chance, and blew it.

The Great Dying and Climate Change

by MARCELO GLEISER
13.7 Cosmos and Culture

The most famous mass extinction is the one that ended the dinosaurs and some 50 percent of life on Earth about 65 million years ago. The culprit was mostly the impact with a large asteroid, about seven miles across, that hit the Yucatán Peninsula in Mexico. I wrote about some of the scary details a couple of months ago.

But the Yucatán event pales in comparison with the mass extinction that happened 252 million years ago, at the end of the Permian period. Scientists estimate that about 95 percent of all marine species, and an unknown "but probably comparable percentage of land species, went extinct in a geological heartbeat," as Alanna Mitchell reported recently in The New York Times.

Although an impact has been proposed as a possible culprit, recent work suggests that the vast die off was related to a lack of oxygen in the water, coupled to an excess of carbon dioxide, which implied in an increase in ocean acidity and water temperatures. A nonlinear feedback from these effects amplified the damage. Corals and sea sponges were devastated, and trilobites were gone.

In a paper for Annual Reviews of Earth and Planetary Sciences, Jonathan Payne, from Stanford University, and Matthew Clapham, from the University of California at Santa Cruz, suggest that the catastrophe coincided with one of Earth's largest continental flood basalt provinces, the Siberian Traps. In other words, a gigantic volcanic eruption launched enormous amounts of gases into the atmosphere, compromising global ocean chemistry, causing climate change and, possibly, the destruction of the ozone layer, which would explain the land extinction. In studying the climate change in the past or present, the coupling of the oceans with the atmosphere is crucial.

The extinction serves as a laboratory to what is going on now, as even larger amounts of CO2 are being launched into the atmosphere, causing the rapid acidification and warming of the oceans. In 1996, Andrew Knoll, a Harvard geologist, and collaborators suggested that increases in atmospheric CO2 had severe consequences for marine life in the late Permian Earth. "Today, humans turn out to be every bit as good as volcanoes at putting carbon dioxide into the atmosphere," he said to the NYT's Mitchell.

Of course, we are not at the late Permian, a time when all continents were united as one, Pangea, and the ocean's chemistry was different. But the lesson is loud and clear for those who choose to hear it: increased concentrations of atmospheric CO2 acidify the oceans and kill marine life. The key difference is that now we are the main culprits and can take measures to attenuate the ensuing changes.

Extinction

The coral reefs are dying. These largest of all earth’s living structures, intricate and brightly colored, home to a vast panoply of colorful fish, mollusks, marine life of all kinds -- the superstructure of biologically diverse ecosystems -- are bleaching white, breaking up, and withering away.

It won’t be the first time that the reefs have died away. In each of the five previous mass extinctions, coral reefs have been severely impacted, taking many millions of years to recover. In this respect, reefs are like the canary in the coal mine. They are a sentinel, whose current calamitous condition foretells the sixth mass extinction, an event many paleontologists believe the earth has already entered.

The cause or causes of earth’s previous mass extinctions have been a matter of intense scrutiny. Hypotheses have ranged from massive volcanism to asteroid strikes. 

The Permian-Triassic extinction of 250 million years ago (Mya), wiped out over 90% of the planet’s marine species. On land, over 70% of reptile, amphibian, insect, and plant species went extinct. It was the most catastrophic of all earth’s extinctions, and may have been triggered by the eruption of the super volcano known as the Siberian Traps, the most massive eruption and lava flow in earth’s history.

The Siberian Traps eruption, which lasted for a million years, added huge amounts of heat, carbon dioxide, and sulfur dioxide to Earth's surface and atmosphere, and the resulting greenhouse effect generated a long warming trend. The climate change triggered by the warming dramatically shifted weather patterns across the globe.

Carbon dioxide has left its fingerprints on all the massive die-offs experienced during earth’s often violent history. J.E.N. Vernon (2008) has pointed out in his article in the journal Coral Reefs, that recent palaeophysiological studies have clearly implicated CO2 in the destruction of most life on earth during the Permian-Triassic extinction.

There is also evidence of a sudden and massive release of methane, perhaps triggered by increased warming. This would have been an example of positive feedback, that is, CO2 causing warming, melting frozen tundra, and thereby releasing methane, which is considered a much more potent greenhouse gas than CO2.

As it happens, Russia’s Siberian tundra is currently melting. Russia has the largest extent of permafrost in the world. Scientists estimate that permafrost covers more than 10 million square kilometers of Russia. The warming planet is melting permafrost in Siberia, and the melting permafrost is releasing methane in much greater quantities than previously thought. Methane is considered 20 times more damaging as a greenhouse gas than carbon dioxide, which means that Siberia is now actively contributing to  warming. Russian scientists believe the melting of Siberian permafrost is irreversible, as the release of green house gases will perpetuate the warming climate.

Experts say Siberian tundra leaking methane in record amounts

And this brings us to the Sixth Mass Extinction -- the one happening now. We’ll address that in a coming blog post.

The Dynamic Between Aerosols and CO2

The Datong Coal-Fired Power Plant in China

Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008. We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects.

Robert K. Kaufmann, et. al, Proceedings of the National Academy of Sciences, June 2, 2011.

Deny, Deny, Deny

People who deny that human activities are contributing to global warming use many arguments in defense of their position, including: increased solar activity (this is a favorite); the imperfect rotation of the earth around its axis (it "wobbles"); and volcanic eruptions spewing greenhouse gases into the atmosphere (they actually throw a lot of dust up that can cause temporary cooling). Other causes have been postulated, including some fairly esoteric ones, such as reversal of the earth's polarity, cosmic rays, and terraforming by extraterrestrials as a prelude to their invasion (they like every place to be like Florida).

As bizarre as the extraterrestrial terraforming may be, another position seems to me to be even more outlandish, viz., humans are just too insignificant a presence to cause such a major change in the environment. One of my critics argued that, "We know the global climate is on a up and down cycle of hundreds of millions of years with mini up and down cycles of hundreds and thousands of years along this path of millions of years." Yeah, I mean what impact can puny humans have on the environment?

Burning the rain forests: http://earthobservatory.nasa.gov/Features/AmazonFireRise/

The Great Pacific Garbage Patch: http://en.wikipedia.org/wiki/Great_Pacific_Garbage_Patch

Species extinction/declining biological diversity: http://www.biologicaldiversity.org/news/press_releases/2009/population-speak-out-02-26-2009.html

Purple Mountains Majesty: http://www.ohvec.org/galleries/mountaintop_removal/007/

Los Angeles, January 29, 2004
I grew up in LA, 1938 -1961, and it didn't look anything like this; damn extraterrestrials!

It's encouraging to see that Americans generally (~70%) have come to accept the fact that the planet is warming, although it's disappointing that there is still so much disagreement over what's causing it. Even when people agree that human activities are causing warming, there is disagreement over what to do about it, if anything. Another of my critics says, "Why bother trying to reduce our emissions, when China, India, and other developing nations are more than offsetting our efforts with their emissions?"

While China is the world's greatest emitter of greenhouse gases (it took over that dubious distinction from the United States in 2006), the US ranks at the top of the GHG leader board in cumulative emissions since 1850, with the EU second. Between them, the US and the EU account for over 55% of cumulative emissions. China is a poor fourth at 7.6%, and India is further down the list at 2.2%. Thus it seems to me disingenuous to tell the world that we're not going to do anything about our emissions because China, and other developing nations, are now emitting GHGs, too.

One of the more unfortunate aspects of dumping so much CO2 into the atmosphere is that for all practical purposes, it never goes away, i.e, "carbon is forever." University of Chicago oceanographer David Archer has stated that, "The climatic impacts of releasing fossil fuel CO₂ to the atmosphere will last longer than Stonehenge, longer than time capsules, longer than nuclear waste, far longer than the age of human civilization so far."

Thus, if we really work hard at decreasing our GHG emissions (instead of increasing them as we're doing now), our best hope is to avoid accumulating more atmospheric CO2 and maybe be lucky enough to avert a "tipping point" crisis, where positive feedback effects overwhelm current climate dynamics and, like flipping a switch, plunge the planet into climate hell.

The Earth's Hadean period, roughly 4.7 billion years ago.

Andrew A. Lacis on Climate Science

Andrew A. Lacis, the NASA climatologist whose 2005 critique of the United Nations climate panel was embraced by bloggers seeking to cast doubt on human-driven climate change, has sent in two more commentaries on the state of climate science.

Human-induced warming of the climate system is established fact.

How do we know this to be true? What does it take to get something established as fact? I will try to explain this quandary here the same way that I explain it to myself.

We have come to understand that nothing happens in this world except as allowed by the laws of physics. What this means is that for every physical action there is going to be a well-defined cause, and a well-defined effect. Quantum mechanical weirdness that operates at atomic scale does not invalidate this physical description of the macroscopic range that is of interest.

Human experience has demonstrated that it is through measurement and physics that we understand the world that we live in. The term “physics” includes also the mathematical description of these laws which permits mathematical models to be constructed to conduct virtual experiments of real-world situations.

In this way, by utilizing global-mean decadal-average quantities, we have come to understand that water vapor accounts for 50 percent of the (33 K, 60 deg F) greenhouse effect. Longwave absorption by clouds contributes 25 percent, and CO2 accounts for 20 percent. The remaining 5 percent of the greenhouse effect is split between methane, N2O, CFCs, ozone, and aerosols. Significantly, CO2 and the minor GHGs do not condense or precipitate at current atmospheric temperatures. This provides a stable reference temperature structure for the fast feedback processes to operate and maintain the amounts of atmospheric water vapor and clouds at their quasi-equilibrium concentrations. Hence the strength of the terrestrial greenhouse is sustained and effectively controlled by the atmospheric temperature floor that is provided by CO2 and the other non-condensing greenhouse gases. (More detail is contained in my Greenhouse Tutorial which is a related supporting commentary.)

The bottom line is that CO2 is absolutely, positively, and without question, the single most important greenhouse gas in the atmosphere. It acts very much like a control knob that determines the overall strength of the Earth’s greenhouse effect. Failure to control atmospheric CO2 is a bad way to run a business, and a surefire ticket to climatic disaster.

My earlier criticism had been that the IPCC AR4 report was equivocating in not stating clearly and forcefully enough that human-induced warming of the climate system is established fact, and not something to be labeled as “very likely” at the 90 percent probability level. It would seem that the veracity of the human-induced warming would hinge on establishing the pedigree of the observed increase in atmospheric CO2. On this point, the IPCC report is crystal clear. Pages 137-140 of IPCC AR4 describe high-precision in situ measurements of atmospheric CO2 at Mauna Loa, documenting the steady increase in CO2 along with its characteristic seasonal fluctuation. These measurements, supplemented by analyses of air bubbles trapped in ice core samples, show unequivocally that atmospheric CO2 has increased from a pre-industrial level of 277 ppm in 1750 to present day concentrations that are approaching 390 ppm.

The IPCC report also shows the corresponding decrease in atmospheric oxygen, thus providing irrefutable verification that the increase in atmospheric CO2 is linked directly to fossil fuel oxidation. In Chapter 7, the IPCC report states it clearly: “the increases in atmospheric carbon dioxide and other greenhouse gases during the industrial era are caused by human activities”. Undoubtedly, volcanic eruptions have contributed some atmospheric CO2, but this can only be miniscule as neither the 1991 Pinatubo eruption (largest of the century), nor the 1986 Lake Nyos CO2 eruption that killed thousands, so much as registered a blip in the Mauna Loa CO2 record.

In view of all this, the IPCC AR4 Chapter 9 Executive Summary states that: “It is likely (66 percent probability) that there has been a substantial anthropogenic contribution to surface temperature increases in every continent except Antarctica since the middle of the 20th century.” How can this be considered anything other than inaccurate and misleading?

To understand climate change, it is necessary to know the radiative forcings that drive the climate system away from its reference equilibrium state. These radiative forcings have been analyzed and evaluated by Hansen et al. (2005, 2007). They include changes in solar irradiance, greenhouse gases, tropospheric aerosols, and volcanic aerosols. Of these forcings, the only non-human-induced forcing that produces warming of the surface temperature is the estimated long-term increase by 0.3 W/m2 of solar irradiance since 1750. Volcanic eruptions are episodic, and can produce strong but temporary cooling. All of the other forcings are directly tied to human activity. When it comes to radiative forcing of global climate change, it is abundantly clear that whether we like it or not, or whether we care to admit it, it is humans who are driving the bus.

Greenhouse Tutorial

In the context of global climate, absorbed solar radiation (about 240 W/m2, with 30 percent of the incident radiation being reflected back to space) is the energy source that keeps the Earth’s surface warm. The Planck radiation law determines that a temperature of 255 K (about 0° F) is needed to have energy balance with the absorbed solar radiation. If the Sun were suddenly turned on, the Earth would begin warming, and would keep warming until it reached a 255 K temperature, at which point it would be radiating 240 W/m2 of thermal energy out to space, in equilibrium with the solar energy input.

The global-mean surface temperature of the Earth is observed to be 288 K (60° F). Why is this so much warmer than the 255 K effective temperature of the thermal radiation emitted to space? The reason is that the Earth has an atmosphere that contains gases that absorb thermal radiation. These gases are distributed throughout the atmosphere, and they also must maintain energy balance on a local scale, meaning that the same amount of radiation absorbed (e.g., from the ground), must be re-emitted (in both upward and downward directions) so as to maintain constant temperature. This radiative process of localized absorption and emission of thermal radiation establishes a temperature gradient within the atmosphere, and in so doing, results in heating the ground surface to a higher temperature than would be the case with no atmosphere. This is the greenhouse effect, and it keeps the surface temperature of the Earth 33 K (60° F) warmer than it would otherwise be for the same 240 W/m2 of solar heating.

It is helpful to analyze the Earth’s energy balance in terms of global-mean and decadal-average quantities, so as not to be distracted by having to worry about local energy balance variations due to regional, clear-sky, cloudy-sky, diurnal, seasonal, and interannual fluctuations. A good climate GCM can be adapted to perform this task.

We know from direct measurement that there are atmospheric constituents that absorb thermal radiation. The most important are: water vapor, cloud particles, and CO2, with smaller contributions coming from methane, N2O, CFCs, ozone, and aerosols. We also know quite accurately the spectral absorption characteristics for the absorbing gases, and how cloud and aerosol particles interact with thermal radiation. This basic knowledge comes from a combination of laboratory measurements and theoretical analyses. This input data is tabulated in the HITRAN database for all significant atmospheric gases, and is available for use in radiative transfer calculations.

It is important to know the relative contribution of each absorbing gas to the total (33 K) greenhouse effect. Precise attribution is difficult because there is significant overlapping absorption with varying degrees of saturation, and there is the need to take into account the vertical structure and time-spatial distribution of absorbers, requiring a good climate GCM with good radiative transfer. The problem is akin to defining the actual weight that is borne by individual support columns of a bridge. We know that collectively the columns must support the entire weight of the bridge, but actual measurements removing one column at a time would be extremely problematic since the weight of the bridge would get redistributed among the remaining columns.

With good mathematical models that accurately represent the radiative interactions of atmospheric interest, we can conduct virtual experiments to determine the radiative contribution of each individual gas within the context of current atmospheric structure. We have performed such experiments for the principal greenhouse gases, clouds, and aerosols using the [Goddard Institute] climate model by systematically inserting, or taking out, each atmospheric constituent one at a time, and recording the corresponding radiative flux change.

These experiments show that water vapor accounts for about 50 percent of the total greenhouse effect. Longwave absorption by clouds contributes 25 percent, and CO2 accounts for 20 percent. The remaining 5 percent of the greenhouse effect is split between methane, N2O, CFCs, ozone, and aerosols. It is significant that CO2 and the minor GHGs do not condense or precipitate at current atmospheric temperatures. This provides a stable temperature structure for the fast feedback processes to operate and maintain the quasi-equilibrium amounts of water vapor and clouds. Hence, the strength of the terrestrial greenhouse effect is effectively sustained and controlled by the atmospheric temperature structure provided by CO2 and the other non-condensing greenhouse gases.

The bottom line is that CO2 is absolutely, positively, and without question, the single most important greenhouse gas in the atmosphere. It acts very much like a control knob that determines the overall strength of the Earth’s greenhouse effect. Failure to control atmospheric CO2 is a bad way to run a business, and a surefire ticket to climatic disaster.

Dr. Andrew A. Lacis
National Aeronautics and Space Administration
NASA Goddard Institute for Space Studies
B.A., Physics, 1963, University of Iowa
M.S., Astronomy, 1964, University of Iowa
Ph.D., Physics, 1970, University of Iowa