Review: Climate Change Expanding Tropics and Sub-Tropical Arid Zones, with Implications

photo: Tim via flickr

A review of peer-reviewed scientific literature done by researchers at Australia’s James Cook University reveals that in the past 25 years there’s been an expansion of the world’s tropical zones and that human activity has contributed to it:

The literature review shows that the areas which climatologists and meteorologists consider to be the tropics (which is defined differently than in geography, where it is defined as within 0 – 23.5 degrees N and S of the Equator) have expanded at minimum 300 kilometers (186 miles).

Future expansion of these zones is harder to predict, but based on what’s now known the planet could see a further spread of the tropical conditions over the next 25 years of between 222-553 kilometers (138-338 miles).

Sub-Tropical Arid Zones Push Into New Areas

The implication of this is that sub-tropical arid zones which border the tropics are being pushed into areas which previously had a more temperate climate, with more pronounced differences in seasonal temperatures and precipitation.

As these areas expand they will begin pushing into more heavily populated areas, with potentially severe impacts on society.

Such areas include heavily populated regions of southern Australia, southern Africa, the southern Europe-Mediterranean-Middle East region, the south-western United States, northern Mexico, and southern South America – all of which are predicted to experience severe drying.If the dry subtropics expand into these regions, the consequences could be devastating for water resources, natural ecosystems and agriculture, with potentially cascading environmental, social and health implications.

Tropical Diseases Spread Into New Areas

Furthermore, the expansion of tropical diseases such as dengue fever could hit areas where the diseases was previously not endemic or where epidemic levels of dengue were previously not present. Researchers said the literature showed that these areas include the southern United States, China, northern Africa in the northern hemisphere, and parts of South America, southern Africa, and most of Australia in the southern hemisphere.

Anthropogenic Causes

As to the cause of all this, the literature is less certain, though the most recent research points to anthropogenic causes. Research published earlier this year in the journalGeophysical Research Letters shows,

…that the observed widening of the tropics can only be accurately replicated by an atmospheric general circulation model that includes direct radiative effects related to human greenhouse gas emissions and stratospheric ozone depletion. Simulation models which did not include anthropogenic radiative effects showed no significant change in the width of the tropics.

Read the full report: Expansion of the Tropics: Evidence and implications (PDF)

“We’re Beginning to See Hints That Ocean Circulation is Changing” – International Polar Year Director

photo: IPY

Over the past year we’ve seen increasing evidence that the effects of climate change in both the Arctic and Antarctic are occurring more quickly than predicted. As a sort year-in-review, the International Polar Year has released The State of Polar Research, 2007-2008. Here are some of IPY’s findings:

Antarctica, Greenland Melting Increases
The Greenland and Antarctic ice sheets are losing mass, contributing to sea level rise.Warming in Antarctica is much more widespread than was previously thought; the rate of ice loss in Greenland also appears to be increasing.

Researchers also found that in the Arctic, during the summers of 2007 and 2008, the minimum extent of year-round sea ice decreased to its lowest level since satellite records began 30 years ago. IPY expeditions recorded an unprecedented rate of sea-ice drift in the Arctic as well. Due to global warming, the types and extent of vegetation in the Arctic shifted, affecting grazing animals and hunting.

Freshening Antarctic Bottom Water
Global warming is affecting Antarctica in ways not previously identified: Above average warming is occurring in the Southern Ocean; freshening of bottom water near Antarctica, the result of increased ice melt there, could affect ocean circulation.

IPY director David Carlson was quoted by AFP as saying,

We’re beginning to get hints of change in ocean circulation, that’ll have a dramatic impact on the global climate system.

Modern Deep-Sea Octopus Ancestors Still Live in Southern Ocean
There’s some other research coming out of IPY that’s interesting: Many present deep-sea octopuses originate from common ancestor species still living in the Southern Ocean. North Atlantic storms are major sources of heat and moisture for the polar regions. The Southern Ocean has a much more colorful and diverse range of life present than previously identified, with some species migrating poleward in response to global warming.

Read the full IPY report: The State of Polar Research

Global Climate Change
It’s Official: Human Activity is Warming Both the Arctic and Antarctic
Two Trillion Tons of Land Ice Melted Since 2003
West Antarctic Glacier Disintegrating Rapidly: First Hand Account

Sea Level Rise Predictions Too Low, No Abrupt Release of Methane: US Climate Change Science Program

Source: “Sea Level Rise Predictions Too Low, No Abrupt Release of Methane: US Climate Change Science Program“, treehugger.com. Science & Technology, Matthew McDermott, 22nd Dec 2008

image: NASA via Space and Astronautics News

Will abrupt climate change happen in the 21st century? The US Climate Change Science Program certainly considers that a possibility and has released a new report, appropriately titled Abrupt Climate Change, detailing its findings.

Defining ‘abrupt’ climate change as those which “can occur over decades or less, persist for decades or more, and cause substantially disruptions to human and natural systems,” the report addresses four major questions (the possibility of abrupt changes in sea level, in land hydrology, in the Atlantic Meridional Overturning Circulation, and in atmospheric methane) and comes to the following conclusions:

IPCC Sea Level Rise Predictions Very Likely Too Low
While the report says rapid and sustained arctic ice loss is likely in the 21st century, current models don’t capture the recent rapid changes seen in Greenland and Antarctica. When these changes are included in climate change models it “will likely lead to sea-level projections for the end of the 21st century that substantially exceed the projections” presented in the latest IPCC report.

Extended Drought Likely in US Southwest
Although the report concludes that “there is no clear evidence to date of human-induced global climate change on North American precipitation amounts,” it also says that subtropical aridity predicted in climate models is likely to intensify and extend into the US Southwest “potentially increasing the likelihood of severe and persistent drought there in the future.” This drying may have already begun but cannot be definitively identified because of “considerable natural variability” of the precipitation patterns in the region.

Ocean Circulation Current Likely to Decrease, Unlikely to Collapse
In case you’ve forgotten parts of An Inconvenient Truth, Atlantic Meridional Overturning Circulation is the feature of the ocean which moves warm, salty water northward in the the upper layers of the Atlantic Ocean and colder water southward in deeper parts of the Ocean.

The USGS concludes that it’s very likely that we will witness a 25-30% decrease in strength of this circulation, but it is very unlikely that the AMOC will become severely weakened of collapse by the end of the 21st century, or collapse because of global warming beyond that time period.

Methane Release Will Accelerate Climate Change, Abrupt Release Very Unlikely
In regards to abrupt release of methane into the atmosphere due to global warming, the report concludes that this appears to be very unlikely, but it is also very likely that methane emissions will increase and that this will accelerate global climate change. A doubling of methane emissions in northern high latitudes “could be realized fairly easily.”

Read the full report: Abrupt Climate Change

Global Climate Change
Permafrost Holds Twice as Much GHGs as Previously Thought
Are We Moving Into Another Era of ‘Abrupt’ Climate Change
Change Coming to Water Politics: Twelve US States Face Extended Drought Conditions
Sea Levels Still Will Rise Because of Global Warming: Just Not as Much as We Thought

Obama Nominates 2 Leading Global Warming Specialists for Key Science Posts in his Administration

 

Harvard physicist John Holdren will be Mr Obama’s scientific adviser while marine biologist Jane Lubchenco will head the US oceanic research body.

Both have advocated greater government action on climate change.

Their appointments have been seen as a sign of Mr Obama’s commitment to tackling environmental issues.

In his weekly address, Mr Obama said that “today, more than ever before, science holds the key to our survival as a planet and our security and prosperity as a nation”.

He said it was “time we once again put science at the top of our agenda” and that he was confident that the US could “lead the world into a new future of peace and prosperity”.

‘Respectful’

Mr Holdren was described by Mr Obama as “one of the most passionate and persistent voices of our time about the growing threat of climate change”.

 

Ms Lubchenco has criticised the Bush administration’s scientific policies

Mr Holdren will become director of the Office of Science and Technology Policy (OSTP) and the co-chair of the Council of Advisers on Science and Technology.

He will share the latter post with Nobel Prize-winning scientist Harold Varmus and Eric Lander, a specialist in human genome research.

Mr Lander’s appointment has been seen as an indication of the importance of genetic research to the Obama administration.

Meanwhile, Ms Lubchenco will direct the National Oceanic and Atmospheric Administration (NOAA) which monitors global weather patterns and ocean currents.

She had criticised the Bush administration earlier this year for not being “respectful” of science.

“I am very much looking forward to a new administration that does respect scientific information and that considers it very seriously in making environmental policies,” she said.

Mr Obama, who takes office on 20 January, has now filled all the posts in the cabinet. However all nominees must still be vetted and approved by the Senate.

Using Space Lasers to Measure Atmospheric Carbon Dioxide

Image via ESA – AOES Medialab

By 2016, we just might have space lasers measuring the carbon dioxide in the atmosphere, and telling us whether or not (or how quickly and for how long) we’re melting the planet.

The Advanced Space Carbon and Climate Observation of Planet Earth – or A-SCOPE for short – is one of six possible missions to be considered for a feasibility study, which could lead to a 2016 launch timeframe for the mission.

The idea is to understand more about how carbon dioxide moves between atmosphere, land and ocean in order to improve how we calculate the impact the greenhouse gas has on the earth, and therefore improve estimates on what we can do about it. In order to accomplish this, the project aims to do something really interesting:

The proposed measuring technique involves two short laser pulses being emitted at two adjacent wavelengths. This results in carbon dioxide being absorbed at one of the wavelengths but not by the other, which serves as a reference. The comparison of the reflected signals from both wavelengths yields the total column concentration of carbon dioxide. This novel approach implies that the return signal depends on the reflectance properties of the area of ground illuminated by the laser.

There is still a lot of footwork to do for this project, but if it is chosen, it could represent a novel way of analyzing carbon dioxide on earth – though it might be long due The work they’re doing also is expected to help out scientists working on laser technology in general.

Other Earth Explorer future missions under consideration include BIOMASS – to take global measurements of forest biomass; CoReH2O – to make detailed observations of key snow, ice and water cycle characteristics; FLEX – to observe global photosynthesis through the measurement of fluorescence; PREMIER – to understand atmospheric processes linking trace gases, radiation, chemistry and climate; and TRAQ – to monitor air quality and long-range transport of air pollutants.

Via Science Daily

More on Measuring Carbon Dioxide
Research Shows that Research Contributes to Global Warming
Venting Our (Carbon Dioxide) Problems into Space
350: The Most Important Number of Your Lifetime

Major Shifts in North Atlantic Ecosystems Driven by ‘Unprecedented’ Climate Change in Last Half-Century

Source: “Major Shifts in North Atlantic Ecosystems Driven by ‘Unprecedented’ Climate Change in Last Half-Century“, Treehugger.com, Science & Technology, Jeremy Elton Jacquot, 8th Nov 2008

The last half-century has witnessed the most dramatic climate-induced ecosystem-level shifts since the advent of human civilization, almost 5,000 years ago, posits a new study published in the November issue ofEcology. Charles Greene, its lead author and an oceanographer at Cornell University, says that current and projected rates of global warming are “unprecedented” in human history and that we could very well see very rapid periods of intense warming in the near future — rivaling the episodes of rapid cooling, during which temperatures dropped by up to 18°F (10°C) over a period of years to decades. (These drastic shifts, or “abrupt” climate changes, could be precipitated by tipping points, such as the mass release of methane from thawing permafrost regions, according to some researchers.)

Large slugs of cold Arctic water drove the shifts
The release of large amounts of cold, low-salinity water into the North Atlantic from melting Arctic ice sheets and glaciers may have caused the most dramatic changes, Greene believes. One example is the introduction of a microscopic algal species from the Pacific Ocean (which has not been seen in the North Atlantic for more than 800,000 years); though it only crossed over the Arctic Ocean a little over a decade ago, it has already spread throughout the North Atlantic region. (Algae are notorious invasive species, and this is probably one of many similar examples.)

Greene and his colleagues did discover that their findings ran counter to many previously widely accepted assumptions. For instance, ecologists had assumed that most species would move northward to seek refuge in cooler areas as the climate warmed; instead, as the colder Arctic waters flowed south all the way to North Carolina, they observed that many northern species actually moved southward.

Ecosystem changes created new “winners” and “losers”
The presence of cooler waters also extended the growth periods of phytoplankton (cooler waters are typically rich in nutrients), which could sometimes alter trophic level dynamics (resulting in new “losers” and “winners”) by introducing a more durable food source. Atlantic cod stocks, which had already been overfished, may have failed to recover in part because of the introduction of colder Arctic waters, which inhibited their growth and reproduction cycles. That, coupled with the arrival of more resilient crustacean species, like the snow crab and shrimp, likely did them in, Greene says.

Is this only the beginning?
Reading this study, I couldn’t help but think of the larger potential threat posed by the mass melting of ice sheets and glaciers in Greenland and the Arctic Ocean: namely, the shutdown of the ocean conveyor belt (which could effectively precipitate another ice age). While it is certainly premature to consider this a possibility — most scientists seem to think it is unlikely to happen — Greene’s study, and others in the same mold, make me worry about all of the climate’s intangibles.

Via: ScienceDaily: ‘Unprecedented’ Warming Drives Dramatic Ecosystem Shifts In North Atlantic, Study Finds

More about climate change
Rising Seas and Powerful Storms Threaten Global Security
Really Abrupt Climate Change Really Happened
Arctic Climate Tipping Point Happening Now! Sea Ice in Its “Death Spiral” Scientist Claims

The Arctic – Fastest August Ice Retreat in History

Images from NSIDC

While we may have narrowly avoided setting a new record high in Arctic ice loss this year, it look as though we may have still hit a dubious milestone: achieving the fastest rate of melting during a four-week period in August than at any time in recent history. Between August 1 and August 31, sea ice declined at a rate of 32,700 square miles per day compared to a rate of roughly 24,400 square miles per day last year. The historical average for that period is 19,700 square miles per day.

As Matthew noted in a recent post, we barely missed passing the record set last year. According to the U.S. National Snow and Ice Data Center (NSIDC), sea ice covered around 4.5 million square kilometers at its lowest point on September 12; by comparison, sea ice covered 4.1 million square kilometers the same time last year.

Not that we should consider this temporary reprieve an auspicious sign. The BBCarticle Matthew cited quoted the NSIDC’s Walt Meier as saying: “(…) so people might be tempted to call it a recovery, but I don’t think that’s a good term, we’re still on a downwards trend towards ice-free Arctic summers.” Indeed, most climate scientists still believe that, if present trends continue, all arctic sea ice will be gone by the end of the century.

Researchers believe that the uptick in melting could be due in part to conditioning taking place in the region; in a study published in Geophysical Research Letters, Jennifer Kay of the National Center for Atmospheric Research (NCAR) and her colleagues found that diminished cloud cover in 2007 allowed more sunlight to reach Earth, which caused more ice melting at the surface and, by warming sea surface temperatures, melting from below as well. This trend is likely to continue as the sea ice, besieged by warming surface water temperatures on one side and a higher albedo effect on the other, becomes thinner and loses the capacity to regenerate.

Via ::ScienceDaily: Arctic Saw Fastest August Sea Ice Retreat On Record, NASA Data Show (news website)

More about Arctic ice cap melting
::Arctic Ice Is Melting At Record Highs
::Melting Arctic Ice Increases Permafrost Thaw Farther Inland Than Previously Thought
::Oh! So Close: Arctic Sea Ice Summer Melt Fails to Set Record in 2008

Source:

“Arctic Just Witnessed Fastest August Ice Retreat in History”, treehugger.com, Science & Technology, Jeremy Elton Jacquot, 27th Sept 2008

Permafrost Holds Twice as Much Greenhouse Gases as Previously Thought: Over 1500 Billion Tons of CO2 and Methane

Image from jurvetson

Following on the heels of a recently published study in the journal Nature Geoscience, which estimated that Arctic permafrost could hold 60% more organic carbon than previously thought, a team of scientists from Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) has found that the planet’s permafrost layers — comprising an area that covers a fifth of Earth’s land mass – store twice as much methane and carbon dioxide as previously believed.

The results of their study, published in the journal Bioscience, state that permafrost layers located at high altitudes contain over 1500 billion tons of CO2 and methane, or twice the amount of GHG currently present in the atmosphere.

Image from Sergei Zimov/CSIRO

Release of even a fraction could greatly increase future temperature rise
While he said it was too early to start making dire predictions about future melting rates, Pep Canadell, a CSIRO atmospheric scientist who co-authored the paper, warned that: “With temperatures in the higher latitudes estimated to rise by as much as eight degrees by the end of this century, the world could experience a major melt of large tracts of permafrost in Canada, Russia, Alaska, Norway, Sweden, Finland and Greenland”.

Consequences could be worsened by positive feedback loop
The great fear among scientists, of course, is that a sudden release of methane and CO2 from the thawing permafrost could perpetuate a dangerous positive feedback cycle in which rising atmospheric GHG levels could accelerate climate change, resulting in more melting and, thus, more emissions. What is clear, in the wake of this and the Nature study, is that climate researchers will have to rejigger their models — which could lead to some sobering revisions in emission targets.

Methane: a potential energy source?
Aside from simply slowing the release of GHG emissions (easier said than done), there is the possibility that some of that trapped methane could be harnessed as an alternative source of energy. Though risky (methane is roughly 21-23 times more potent a GHG than CO2), Japan, Canada and a few other countries have been working on finding economical ways to safely extract the methane hydrates from wells in the permafrost. For now, however, it’s probably best to focus on the main issue at hand: drastically reducing our current emission production.

Via ::Climate Change Blog: Permafrost Perma-Emergency (blog)

More about permafrost
::60% More Greenhouse Gases Trapped in Permafrost Than Previously Thought
::Melting Arctic Ice Increases Permafrost Thaw Farther Inland Than Previously Thought
::Researchers Extract Permafrost-Locked Methane from Gas Hydrates, Potentially Paving Way for Large New Energy Source

Source:

“Permafrost Holds Twice as Much GHGs as Previously Thought: Over 1500 Billion Tons of CO2 and Methane”, treehugger.com, Science & Technology, Jeremy Elton Jacquot, 13th Sept 2008

New Gravity-Mapping, Climate Predicting Satellite set to launch from Russia

 

Despite the major improvements made in satellite technology and modeling over the past few years, predicting future climate change remains a tricky matter. Taking into account the often conflicting reams of data provided by researchers and monitoring technologies results in the creation of imperfect models that inevitably fail to accurately represent all aspects of the changing climate.

It is in the hope of tackling this vexing problem that scientists from the European Space Agency (ESA) are preparing to launch the Gravity field and steady-state Ocean Circulation Explorer (GOCE), which will help improve measurements of the Earth’s gravitational field and, in turn, improve predictions about climate change. The satellite will help climate scientists arrive at a more accurate picture of the ocean currents, The Guardian’s James Randerson reports, by comparing their surface shape with the fluctuations in the planet’s gravitational field.

Image from the ESA

GOCE, which will remain in orbit for around 20 months, will complete a map of the Earth’s gravitational field once every 70 days; it will orbit from pole to pole at an altitude of 160 miles — low by most satellites’ standards, but necessary for it to precisely record the minute changes in gravity that regularly occur.

To measure these tiny variations, GOCE is equipped with 3 pairs of ultra-sensitive accelerometers arranged in 3-D. Their particular arrangement allows them to respond to the planet’s gravitational acceleration differently and, in so doing, simultaneously measure 6 unique, but complementary, components of its gravity field.

The “Formula 1″ of spacecrafts (that’s what the ESA is calling it), GOCE will become the most advanced gravity space mission to data when it launches next month. Here’s a brief snippet explaining how GOCE works from the ESA’s latest press release:

Over its lifetime of about 20 months, GOCE will map these global variations in the gravity field with extreme detail and accuracy. This will result in a unique model of the geoid, which is the surface of equal gravitational potential defined by the gravity field – crucial for deriving accurate measurements of ocean circulation and sea-level change, both of which are affected by climate change. GOCE-derived data is also much needed to understand more about processes occurring inside the Earth and for use in practical applications such as surveying and levelling.Since the gravitational signal is stronger closer to Earth, the ‘arrow-like’, five-metre long GOCE satellite has been designed to cut through of what remains of the Earth’s atmosphere at just 250 km above the surface of the planet. This low-orbiting spacecraft is the first mission to employ the concept of gradiometry – the measurement of acceleration differences over short distances between an ensemble of proof masses inside the satellite.

 

Via ::Climateer Investing: New Satellite to Predict Future Climate Change (blog) and::The Daily Galaxy: New Satellite to Predict Future Climate Change (blog)

More about satellites
::Satellite Images Reveal Two of Greenland’s Biggest Glaciers Are Losing More Ice
::Brazil to Develop Satellite to Monitor Deforestation, Urban Expansion
::NASA Satellite Could Make Floating Ocean Wind Farms Possible

Source:

“New gravity-mapping, climate-predicting satellite set to launch from Russia”, treehugger.com, Science & Technology, Jeremy Elton Jacquot, 12th Sept 2008