Global Climate Change: Key Indicators

Time Series Data_CO2

Carbon dioxide (CO2) is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. The chart on the left shows the CO2 levels in the Earth’s atmosphere during the last three glacial cycles, as reconstructed from ice cores. The chart on the right shows CO2 levels in recent years, corrected for average seasonal cycles.

Source :NASA

Timing a Rise in Sea Level

NASA, via Reuters
NASA, via Reuters

Thirty-five years ago, a scientist named John H. Mercer issued a warning. By then it was already becoming clear that human emissions would warm the earth, and Dr. Mercer had begun thinking deeply about the consequences.

His paper, in the journal Nature, was titled “West Antarctic Ice Sheet and CO2 Greenhouse Effect: A Threat of Disaster.” In it, Dr. Mercer pointed out the unusual topography of the ice sheet sitting over the western part of Antarctica. Much of it is below sea level, in a sort of bowl, and he said that a climatic warming could cause the whole thing to degrade rapidly on a geologic time scale, leading to a possible rise in sea level of 16 feet.

While it is clear by now that we are in the early stages of what is likely to be a substantial rise in sea level, we still do not know if Dr. Mercer was right about a dangerous instability that could cause that rise to happen rapidly, in geologic time. We may be getting closer to figuring that out.

An intriguing new paper comes from Michael J. O’Leary of Curtin University in Australia and five colleagues scattered around the world. Dr. O’Leary has spent more than a decade exploring the remote western coast of Australia, considered one of the best places in the world to study sea levels of the past.

The paper, published July 28 in Nature Geoscience, focuses on a warm period in the earth’s history that preceded the most recent ice age. In that epoch, sometimes called the Eemian, the planetary temperature was similar to levels we may see in coming decades as a result of human emissions, so it is considered a possible indicator of things to come.

Examining elevated fossil beaches and coral reefs along more than a thousand miles of coast, Dr. O’Leary’s group confirmed something we pretty much already knew. In the warmer world of the Eemian, sea level stabilized for several thousand years at about 10 to 12 feet above modern sea level.

The interesting part is what happened after that. Dr. O’Leary’s group found what they consider to be compelling evidence that near the end of the Eemian, sea level jumped by another 17 feet or so, to settle at close to 30 feet above the modern level, before beginning to fall as the ice age set in.

In an interview, Dr. O’Leary told me he was confident that the 17-foot jump happened in less than a thousand years — how much less, he cannot be sure.

This finding is something of a vindication for one member of the team, a North Carolina field geologist, Paul J. Hearty. He had argued for decades that the rock record suggested a jump of this sort, but only recently have measurement and modeling techniques reached the level of precision needed to nail the case.

We have to see if their results withstand critical scrutiny. A sea-level scientist not involved in the work, Andrea Dutton of the University of Florida, said the paper had failed to disclose enough detailed information about the field sites to allow her to judge the overall conclusion. But if the work does hold up, the implications are profound. The only possible explanation for such a large, rapid jump in sea level is the catastrophic collapse of a polar ice sheet, on either Greenland or Antarctica.

Dr. O’Leary is not prepared to say which; figuring that out is the group’s next project. But a 17-foot rise in less than a thousand years, a geologic instant, has to mean that one or both ice sheets contain some instability that can be set off by a warmer climate.

That, of course, augurs poorly for humans. Scientists at Stanford calculated recently that human emissions are causing the climate to change many times faster than at any point since the dinosaurs died out. We are pushing the climate system so hard that, if the ice sheets do have a threshold of some kind, we stand a good chance of exceeding it.

Another recent paper, by Anders Levermann of the Potsdam Institute for Climate Impact Research in Germany and a half-dozen colleagues, implies that even if emissions were to stop tomorrow, we have probably locked in several feet of sea level rise over the long term.

Benjamin Strauss and his colleagues at Climate Central, an independent group of scientists and journalists in Princeton that reports climate research, translated the Levermann results into graphical form, and showed the difference it could make if we launched an aggressive program to control emissions. By 2100, their calculations suggest, continuing on our current path would mean locking in a long-term sea level rise of 23 feet, but aggressive emission cuts could limit that to seven feet.

If you are the mayor of Miami or of a beach town in New Jersey, you may be asking yourself: Exactly how long is all this going to take to play out?

On that crucial point, alas, our science is still nearly blind. Scientists can look at the rocks and see indisputable evidence of jumps in sea level, and they can associate those with relatively modest increases in global temperature. But the nature of the evidence is such that it is hard to tell the difference between something that happened in a thousand years and something that happened in a hundred.

On the human time scale, of course, that is all the difference in the world. If sea level is going to rise by, say, 30 feet over several thousand years, that is quite a lot of time to adjust — to pull back from the beaches, to reinforce major cities, and to develop technologies to help us cope.

But if sea level is capable of rising several feet per century, as Dr. O’Leary’s paper would seem to imply and as many other scientists believe, then babies being born now could live to see the early stages of a global calamity.

Source

How is climate change shaping the type of space exploration NASA does?

Image by Jenny Mottar, NASA Headquarters
Image by Jenny Mottar, NASA Headquarters

As global climate change becomes more evident, NASA’s satellite program for studying and monitoring our home planet becomes increasingly important. There are two key areas toward which NASA satellite measurements can contribute:

1.  Monitoring changes in the Earth’s climate.  Global climate change occurs slowly relative to weather and even to the change of seasons throughout the year. Changes known to be related to global climate change–increased atmospheric carbon dioxide and other greenhouse gases (including water vapor), sea level rise, and the melting of Arctic sea ice and the Greenland and Antarctic ice sheets–are so gradual that it takes many years, even decades, to characterize and quantify them.

Given that satellite missions typically last on the order of three to 10 years, NASA often needs to consider launching copies of some instruments, as current versions age and fail. Continuity in our satellite observations is important for maintaining long records of key climate indicators, such as those listed above.  Having long and continuous records of these is critical for monitoring the effects of climate change, helping determine how we can best adapt to them, and assessing whether measures to limit its effects are working as expected.

2.  Improving our understanding of global climate change key processes. Simply monitoring some of the climate change indicators listed above doesn’t provide enough information for scientists to fully understand and characterize the problem and consequences.

For example, only observing sea level rise doesn’t illuminate all the key processes that might be involved in determining the rate at which it is rising; these include sea level rise, the melting of ice sheets and glaciers, warming of the ocean, the continents’ and shorelines’ slow response to ice sheet melting and sea level rise, etc.  Similarly, it is critical to understand how water vapor and clouds respond to climate change, as these help determine the amount of future temperature warming that might be expected to result from increasing the amount of greenhouse gases in the atmosphere.

Knowing “how the Earth’s climate works” is vital to making projections of future warming and the associated impacts using very sophisticated computer models of the Earth’s climate.  For such projections to be useful, they have to accurately represent the Earth’s climate system.

Thus, some of NASA’s satellite program focuses on developing new observations to illuminate how the Earth’s climate system works and to reduce uncertainties in global models used for climate projection.

The above is from Dr. Duane Waliser, who specializes in climate dynamics and modeling. He is the chief scientist of JPL’s Earth Science and Technology Directorate and an adjunct professor in the Atmospheric and Oceanic Sciences Department at UCLA.

Source

 

Antarctica Without Ice and Snow

What does Antarctica look like in its underwear?
What does Antarctica look like in its underwear?

 

A team at the British Antarctic Survey working with NASA pulled together decades of data to show us a virtual map without all the ice and snow. For the first time, the continent’s bare topography is revealed.

VIDEO: Mythical Viking Sunstone is Real

The Bedmap2 is a new virtual map created from substantial amounts of data that included recent measurements from airborne missions as well as satellites. The project, led by British Antarctic Survey scientist Peter Fretwell, relied on NASA’s Operation IceBridge, which has recorded Antarctica’s surface elevations, ice shelf limits and ice thickness. The new map led to some unexpected discoveries about the southernmost continent.

Not only is the volume of ice in Antarctica 4.6 percent greater than previously thought but the deepest point turns out to be under Byrd Glacier — about 1,300 feet deeper than the spot that had been called the deepest, according to research Fretwell and his colleagues recently published in the scientific journal The Cryosphere (PDF).

The Bedmap2 could also help humanity in the future. Study co-author Hamish Pritchard pointed out that understanding the actual height and thickness of the ice as well as the landscape underneath will be fundamental to modelling the ice sheet. ”Knowing how much the sea will rise is of global importance, and these maps are a step towards that goal,” he told the British Antarctic Survey.

NEWS: Boom! Super Seismo-Sonic Earthquakes Are Real

Over at NASA, interactive images show how the continent currently appears, and using a slider you can see the Bedmap2 topography below. There’s also a feature comparing the original Bedmap from 10 years ago with the newest one. Visualizing what’s below the frozen landscape is impressive, as long as it doesn’t end up being a snapshot of our planet’s shirtless future.

Image: Antarctica’s underlying topography in the Bedmap2. Credit: NASA Goddard’s Scientific Visualization Studio.

 

The Rising Cost of Carbon Pollution

cost of carbon

 

Every ton of carbon dioxide we emit this year will cost the world $35 in health problems, wildfires, loss of agricultural productivity, and other disasters, according to the U.S. government. It had computed $21 a ton in 2010.

The value, known as the social cost of carbon – and which can equal the carbon tax — will rise for every additional ton of carbon dioxide we emit. It will be $43 in 2020 and $71 in 2050.

The world emitted 34 billion tons of carbon dioxide in 2011.

The U.S. government routinely uses social cost when designing regulations such as fuel efficiency standards for cars. The value is calculated by the Interagency Working Group on Social Cost of Carbon, composed of 12 government agencies, and was released on May 31.

A price for carbon is needed because we are shortsighted and are best at dealing with immediate problems. But the effects of climate change are not immediate. The extreme weather and high temperatures we are experiencing now are the result of the past emissions, and our present emissions will affect us decades into the future.

Most of us will not live through the worst of it. So, how much is it worth to the average American today to lessen climate change for future generations? It is an ethical question that gets worked out by economists.

Some of them disagree quite vehemently with the government’s calculations. Economists have redone the calculations and found that the actual social cost could be up to 12 times as large as the government’s 2010 estimate.

The government has increased social cost value to $35 this year because it has better knowledge of climate change effects, including sea level dynamics and the economic effects of sea level rise.

IMAGE: A dragonfly trapped in tar sands exposed in a road cutting north of Fort McMurray, Alberta, Canada, the center of the tar sands industry. The tar sands is the world’s largest industrial project and the most environmentally destructive. Carbon emissions from the tar sands is fueling climate change.

Source

Global Floods of the Future

Projected return period (in years) in the 21st Century for river discharges matching what in the 20th Century were 100-year floods.
Projected return period (in years) in the 21st Century for river discharges matching what in the 20th Century were 100-year floods.

scientists who have employed no fewer than 11 separate climate models to study the decades ahead.

Play Video
The daring rescue of an elderly woman from a flooded river in Missouri is caught on video.

“Floods are among the most major climate-related disasters,” writes Yukiko Hirabayashi of The University of Tokyo and lead author of a paper in the June 9 issue of the journal Nature Climate Change. “In the past decade, reported annual losses from floods have reached tens of billions of U.S. dollars and thousands of people were killed each year.”

This, and the fact that the primary worldwide organization that studies such things–the Intergovernmental Panel on Climate Change (IPCC)–has pointed out the need for better projections of river flooding, served as motivation for the new study.

What the researchers found was an increase in the frequency of flooding rivers in Southeast Asia, Peninsular India, eastern Africa and the northern half of the Andes. At the same time, river flood frequencies will drop in parts of northern and Eastern Europe, Anatolia, Central Asia, central North America and southern South America.

In terms of the number of people exposed to flood risks, they found that depends on the temperatures to which things heat up. With a 2-degree Celsius rise in temperature, about 27 million people will be exposed to more floods. With a 4 degrees C warming the exposure rises to 62 million and at 6 degrees C it is up to 93 million people.

The climate models were also used to study the outlets of some river basins. There they saw the frequency of floods increasing during the twenty-first century in just about every selected rivers in South Asia, Southeast Asia, Oceania, Africa and Northeast Eurasia. They also predict that what were considered 100-year floods in the 20th century will occur every 10 to 50 years in the 21st century.

“This is very important and useful information, and shows that policy makers should take climate change into account when developing adaptation strategies,” said flood researcher Brenden Jongman of VU University of Amsterdam. “Also, the analysis of changes in flood frequency on a global scale is very important – this shows that in many developing countries the frequency of extreme events might be increasing.”

While the latest IPCC report still states that ‘global warming might lead to higher flood frequencies and intensities, Jongman explained, this work finally puts real numbers on the flooding.

Source

Climate Change Has Shifted the Location

Climate Change Has Shifted the Locations of Earth’s North and South Poles

 Climate Change Has Shifted the Locations
Climate Change Has Shifted the Locations

Increased melting of the Greenland Ice Sheet and other ice losses worldwide have helped to move the North Pole several centimeters east each year since 2005

Global warming is changing the location of Earth’s geographic poles, according to a new study in Geophysical Research Letters.

Researchers at the University of Texas, Austin, report that increased melting of the Greenland ice sheet — and to a lesser degree, ice loss in other parts of the globe — helped to shift the North Pole several centimeters east each year since 2005.

“There was a big change,” says lead author Jianli Chen, a geophysicist.

From 1982 to 2005, the pole drifted southeast toward northern Labrador, Canada, at a rate of about 2 milliarcseconds —or roughly 6 centimetres — per year. But in 2005, the pole changed course and began galloping east toward Greenland at a rate of more than 7 milliarcseconds per year.

Scientists have long known that the locations of Earth’s geographic poles aren’t fixed. Over the course of the year, they shift seasonally as the Earth’s distributions of snow, rain, and humidity change. “Usually [the shift] is circular, with a wobble,” says Chen.

But underlying the seasonal motion is a yearly motion that is thought to be driven in part by continental drift. It was the change in that motion that caught the attention of Chen and his colleagues, who used data collected by NASA’s Gravity Recovery and Climate Experiment (GRACE) to determine whether ice loss had shifted and accelerated the yearly polar drift.

GRACE’s twin probes measure changes in the Earth’s gravity field, which can be used to track shifts in the distribution of water and ice.  Chen’s team used GRACE data to model how melting icecaps affect Earth’s mass distribution. They found that recent accelerated ice loss and associated sea-level rise accounted for more than 90% of the post-2005 polar shift.

The results suggest that tracking polar shifts can serve as a check on current estimates of ice loss, says Erik Ivins, a geophysicist at NASA’s Jet Propulsion Laboratory in Pasadena, California. When mass is lost in one part of a spinning sphere, its spin axis will tilt directly toward the position of the loss, he says — exactly as Chen’s team observed for Greenland. “It’s a unique indicator of the point where the mass is lost,” says Ivins.

Scientists can locate the north and south poles to within 0.03 milliarcseconds by using Global Positioning System measurements to determine the angle of the Earth’s spin. Knowing the motion of the poles constrains estimates of ice loss made by other methods, Chen says.

And that could help scientists watching Earth’s ice bridge a likely data gap between GRACE and its replacement, GRACE II, which NASA has scheduled for launch in 2020. Researchers may also be able to use longstanding records of polar drift to improve estimates of ice loss and growth before the advent of satellite monitoring.

Chen estimates that data on polar shifts goes back roughly a century, well before the advent of Earth-monitoring satellites. “We don’t have a long record of measuring the polar ice sheet,” he says. “But for polar motion, we have a long record.”

The article was first published in Nature magazine on May 14, 2013.

Entering unknown territory: Carbon dioxide milestone passed

Entering unknown territory

Carbon dioxide milestone passed
Climate change chronicles from NASA
Climate change chronicles from NASA

Imagine there are no people. Imagine a planet where the sea level is about five to 40 meters (16 to 131 feet) higher than normal. Imagine a planet that is hotter and wetter. Imagine, worldwide, it’s roughly 3 to 4 degrees Celsius (5.4 to 7.2 degrees Fahrenheit) warmer than today. And the North and South poles are even warmer still – as much as 10 degrees Celsius (18 degrees Fahrenheit) hotter than today.

Welcome to the Pliocene. That was the Earth about three to five million years ago, very different to the Earth we inhabit now. But in at least one respect it was rather similar. This is the last time that carbon dioxide (CO2) levels were as high as they are today.

On May 9, 2013, CO2 levels in the air reached the level of 400 parts per million (ppm). This is the first time in human history that this milestone has been passed. A preliminary daily average reading of 400.03 ppm was reported by the U.S. National Oceanic and Atmospheric Administration (NOAA), which operates the Mauna Loa Observatory in Hawaii where these measurements are made. While 400 sounds like just another number whose meaning is hard to grasp – similar to, say, world population recently hitting seven billion – these things do resonate, says Dr. Gavin Schimdt of NASA’s Goddard Institute for Space Studies. “People respond to anniversaries – why is 10 years after 9/11 more worthy of note than nine or 11 years? The importance of crossing 400 ppm is simply that it allows us to mark the occasion, and to demonstrate to the future that we knew where we were headed.”

CO2 is the most important man-made greenhouse gas, which means (in a simple sense) that it acts like a blanket trapping heat near the surface of the Earth. It comes from the burning of fossil fuels such as coal, oil and natural gas, as well as deforestation. The level of CO2 in the atmosphere has risen from around 317 ppm in 1958 (when Charles David Keeling began making his historical measurements at Mauna Loa) to 400 ppm today. It’s projected to reach 450 ppm by the year 2040.

One of the problems is that CO2 lingers, both in the atmosphere and in the oceans (where it is being absorbed and acidifying the waters, with potentially big impacts on marine life). More than half of the CO2 is removed from the atmosphere within a century, but about 20 percent remains in the air for many thousands of years. Because of slow removal processes, even if we massively reduced our emissions of CO2 right now, atmospheric CO2 would continue to increase in the long-term. The CO2 we emit today, and that we have emitted since the advent of the Industrial Revolution, has long-term consequences that future generations will have to live with.

Some scientists, like NASA’s James Hansen, argue that CO2 must be limited to around 350 ppm in order to prevent “dangerous” climate change. As Hansen wrote in a 2008 paper, “If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced … to at most 350 ppm.”

To some, crossing the threshold of 400 ppm is a signal that we are now firmly seated in the “Anthropocene,” a human epoch where people are having major and lasting impacts on the planet. Because of the long lifetime of CO2, to others it means we are marching inexorably towards a “point of no return,” into territory that is unknown for the human race.

Written by : Amber Jenkins, NASA Jet Propulsion Laboratory.