Where is the global warming?

 

As climate change has warmed the Earth, oceans have responded more slowly than land environments. But scientific research is finding that marine ecosystems can be far more sensitive to even the most modest temperature change.

Global warming caused by human activities that emit heat-trapping carbon dioxide has raised the average global temperature by about 1°F (0.6°C) over the past century. In the oceans, this change has only been about 0.18°F (0.1°C). This warming has occurred from the surface to a depth of about 2,300 feet (700 meters), where most marine life thrives.

Perhaps the ocean organism most vulnerable to temperature change is coral. There is evidence that reefs will bleach (eject their symbiotic algae) at even a slight persistent temperature rise. Bleaching slows coral growth, makes them susceptible to disease, and can lead to large-scale reef die-off.

Other organisms affected by temperature change include krill, an extremely important link at the base of the food chain. Research has shown that krill reproduce in significantly smaller numbers when ocean temperatures rise. This can have a cascading effect by disrupting the life cycle of krill eaters, such as penguins and seals—which in turn causes food shortages for higher predators.

Higher Sea Levels

When water heats up, it expands. Thus, the most readily apparent consequence of higher sea temperatures is a rapid rise in sea level. Sea level rise causes inundation of coastal habitats for humans as well as plants and animals, shoreline erosion, and more powerful storm surges that can devastate low-lying areas.

Stronger Storms

Many weather experts say we are already seeing the effects of higher ocean temperatures in the form of stronger and more frequent tropical storms and hurricanes/cyclones. Warmer surface water dissipates more readily into vapor, making it easier for small ocean storms to escalate into larger, more powerful systems.

These stronger storms can increase damage to human structures when they make landfall. They can also harm marine ecosystems like coral reefs and kelp forests. And an increase in storm frequency means less time for these sensitive habitats to recover.

Other Consequences

Warmer sea temperatures are also associated with the spread of invasive species and marine diseases. The evolution of a stable marine habitat is dependent upon myriad factors, including water temperature. If an ecosystem becomes warmer, it can create an opportunity where outside species or bacteria can suddenly thrive where they were once excluded. This can lead to forced migrations and even species extinctions.

Warmer seas also lead to melting from below of polar ice shelves, compromising their structural integrity and leading to spectacular shelf collapses. Scientists also worry that warmer water could interrupt the so-called ocean conveyor belt, the system of global currents that is largely responsible for regulating Earth's temperature. Its collapse could trigger catastrophically rapid climate changes.

Will It Continue?

The only way to reduce ocean temperatures is to dramatically reign in our emission of greenhouse gases. However, even if we immediately dropped carbon dioxide emissions to zero, the gases we've already released would take decades or longer to dissipate.

From: The Ocean, National Geographic

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.

Global Warming and the Oceans

Excellent presentation on global warming by Naomi Oreskes.

The Current Mass Extinction

“Once there were brook trout in the streams in the mountains. You could see them standing in the amber current where the white edges of their fins wimpled softly in the flow. They smelled of moss in your hand. Polished and muscular and torsional. On their backs were vermiculate patterns that were maps of the world in its becoming. Maps and mazes. Of a thing which could not be put back. Not be made right again. In the deep glens where they lived all things were older than man and they hummed of mystery.”
(Cormack McCarthy, The Road)

I have described in an earlier post a rapid (in geologic terms) loss of species and a deteriorating environment, but the possibility that we, the human race, a "weedy" species, like dandelions in our lawns, may survive. And after many generations, our progeny may have no memory, no notion, of how much is missing from the impoverished world we have bequeathed them.

But there is another possibility. One in which things happen too fast for us to adapt, and along with the vast majority of other life on earth, we follow the Passenger Pigeon into extinction.

Climate scientists today are concerned about the so-called "tipping point," the moment at which a dynamical system, such as the earth, that has been changing slowly and predictably will suddenly "flip" to a state inimical to life as we know it. With respect to the climate, this can happen as a result of certain changes inducing other changes, which in turn, induce others and reinforce the original forcing function. This is a case of positive feedback not being a good thing.

Consider sea ice, for example, an implacable force of nature that covers an area on earth about two and one half times the size of Canada. Sea ice has a very significant impact on climate change. The ice has a bright surface that reflects sunlight back into space, so areas covered by sea ice don't absorb much solar energy, and temperatures in the polar regions remain relatively cool.

As warming temperatures melt sea ice, as they are doing now, fewer bright surfaces are available to reflect sunlight back into space, more solar energy is absorbed at the surface, and temperatures rise. As sea ice melts further, more solar energy is absorbed, and more sea ice melts.This chain of events starts a cycle of warming and melting, leading to greater and greater warming and continued loss of sea ice, with predictable results; the dynamics of sea ice freezing and melting reaches a tipping point where freezing can’t keep up with melting and the sea ice disappears, removing a vital component in the earth’s homeostasis -- its ability to maintain an equilibrium.

There’s another type of “melting” that’s taking place as a result of rising global temperatures, and that’s the thawing of the permafrost covering the earth’s tundra. Tundra is located at the top of the northern hemisphere in Europe, Asia and North America. It covers 20% of the earth's surface just below the polar cap. Permafrost trapped carbon buried since the Pleistocene era. When permafrost melts, that carbon comes bubbling to the surface of lakes, and dissipating into the atmosphere as methane, a greenhouse gas 23 times more potent than carbon dioxide. And the permafrost is melting -- at five times the rate previously thought.

The rapid release of methane will accelerate the greenhouse gas trapping effect that's currently warming the earth, and that will in turn, increase the rate at which sea ice is disappearing. And that takes us back to the role of sea ice in reflecting solar energy back into the atmosphere, instead of absorbing it in the ocean. You get the drift.

Another type of tipping point occurs when a particular ecosystem sustains so much damage that it can no longer sustain itself. This is what's happening in the Amazon Rainforest.

The dense forests of the Amazon soak up more than one-quarter of the world's atmospheric carbon, making it a critically important buffer against global warming. But a warming climate combined with unchecked slash and burn clearing is bringing the rainforest to the brink of disaster.

Billions of trees died in the record drought that struck the Amazon in 2010, and agriculture, and urban development along with the road building that accompanies it are destroy billions of additional trees and the essential and fragile ground cover that makes the rainforest possible.

The Amazon is but one of ten threatened forests on the earth. If forests lose their ability to act effectively as carbon sinks, additional green house gases will contribute to accelerating global warming, which will subject the earth to further extreme droughts, loss of additional trees, and runaway climate change.

Biologists who believe the earth is experiencing its sixth mass extinction identify five primary direct drivers in addition to climate change, all are the result of human behavior: habitat loss, invasive species, pollution, over-exploitation of resources, and the factor that magnifies all the others—human overpopulation.

According to studies, at least half of all plant and animal species are likely to disappear in the wild within the next 30-40 years, including many of the most familiar and beloved large mammals: elephants, polar bears, chimpanzees, gorillas and all the great apes, all the big cats, and many, many others.

Bird species are similarly imperiled, songbird populations have declined by 50% in the last 40 years. One out of every eight species of plant life worldwide and almost one third of the plant species within the United States already face extinction.

Populations of large ocean fish have declined by 90% since the 1950s. All around the world, birds, reptiles, mammals, amphibians, fish, and invertebrates, as well as trees, flowering plants, and other flora, are all in steep decline.

As disturbing as this rapid decline of species and its attendant support for a sixth extinction event is, there's an even more disturbing, even terrifying prospect -- sudden destabilization of the earth system with imminent death and destruction across all species, including most especially, human. Is this even remotely possible? You're damn right it is.

 I'll discuss this in a future post.