Research Suggests Upper Troposphere Warming (Above Tropics)

From: physicsworld.com – May 28, 2008

Research performed in the US has provided insight on one of the lasting controversies surrounding climate models: whether or not the upper troposphere is warming. Climate models have long predicted that the upper troposphere — a region of the Earth’s atmosphere that lies beneath the stratosphere at an altitude of 10–12 km — should be warming at least as fast as the surface. However, since the 1970s temperature measurements carried out by weather balloons have found the lower-troposphere temperature to be fairly constant. This conclusion was backed up in 1990, when researchers used data taken from satellites to measure temperature changes in the troposphere.

For a while climate scientists have known that weather-balloon instruments are affected by the warming effect of the Sun’s light. They have also struggled to interpret the extent to which the satellite data of the troposphere could be influenced by the stratosphere. But the awareness of these uncertainties has not made it any clearer as to what temperature changes, if any, are taking place in the upper troposphere. Now, Robert Allen and Steven Sherwood of Yale University have used wind data taken from weather balloons as a proxy for direct temperature measurements to give the first conclusive evidence that the upper troposphere has been warming after all. Although they are an indirect measure of temperature, these wind records can be backed up by satellite and ground instruments, making them more reliable than existing direct temperature measurements.

Wind data were obtained from 341 weather-balloon stations — 303 in the northern hemisphere and 38 in the southern hemisphere — covering a period from 1970 to 2005. The data were converted to temperature measurements, using a relationship known as the “thermal-wind equation”, which describes how vertical gradients in wind speed change with horizontally varying temperature. They found that the maximum warming has occurred in the upper troposphere above the tropics at 0.65 ± 0.47 °C per decade.

“This research really does show the tropical troposphere has been warming over the past three decades,” says Benjamin Santer of Lawrence Livermore National Laboratory. “And it will, I hope, put this controversy of weather balloon and satellite data to rest.” Santer, who was one of the lead authors of the 1995 report by the Intergovernmental Panel on Climate Change, thinks the next step is to confirm Allen and Sherwood’s findings with direct temperature records. These, he explains, must be taken with advanced weather-balloon instruments that can be calibrated against older models to remove biases. “The approach by Allen and Sherwood is a promising start,” says John Lanzante of Princeton University. “But more confidence can be established as other investigations further scrutinize the wind data and method used to translate winds into temperature-equivalent measures.”

Full Article: http://physicsworld.com/cws/article/news/34398

Related posts:

> http://www.sustainabilityforum.com/forum/climate-change/2606-research-suggests-upper-troposphere-warming-above-tropics.html

> http://www.geo-earth.com/forums/index.php?showtopic=7523
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Destruction of Greenhouse gases over Tropical Atlantic

Environmental Research Web – July 02, 2008

Large amounts of ozone – around 50% more than predicted by the world's state-of-the-art climate models – are being destroyed in the lower atmosphere over the tropical Atlantic Ocean. This discovery has particular significance because ozone in the lower atmosphere acts as a greenhouse gas and its destruction also leads to the removal of the third most abundant greenhouse gas; methane.

The findings come after analysing the first year of measurements from the new Cape Verde Atmospheric Observatory, recently set up by British, German and Cape Verdean scientists on the island of São Vicente in the tropical Atlantic. Alerted by these Observatory data, the scientists flew a research aircraft up into the atmosphere to make ozone measurements at different heights and more widely across the tropical Atlantic. The results mirrored those made at the Observatory, indicating major ozone loss in this remote area.

So, what's causing this loss? Instruments developed at the University of Leeds, and stationed at the Observatory, detected the presence of the chemicals bromine and iodine oxide over the ocean for this region. These chemicals, produced by sea spray and emissions from phytoplankton (microscopic plants in the ocean), attack the ozone, breaking it down. As the ozone is destroyed, a chemical is produced that attacks and destroys the greenhouse gas methane. Up until now it has been impossible to monitor the atmosphere of this remote region over time because of its physical inaccessibility. Including this new chemistry in climate models will provide far more accurate estimates of ozone and methane in the atmosphere and improve future climate predictions.

Full Article: http://environmentalresearchweb.org/cws/article/yournews/34845

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> http://www.its2hot.in/viewtopic.php?f=49&t=254&p=530#p530

> http://www.sustainabilityforum.com/forum/climate-change/2692-destruction-greenhouse-gases-over-tropical-atlantic.html

> http://debateclimatechange.talk-forums.com/science-of-climate-change-f1/natural-destruction-of-greenhouse-gases-over-tropical-atlantic-t33.htm
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How real clouds respond to aerosols

Environmental Research Web - August 13, 2008

Aerosols have been increasing in the atmosphere since the industrial revolution. One of their indirect effects, called the cloud albedo effect, is to increase the amount of solar radiation reflected back to space by clouds. Now, using detailed satellite observations, NASA scientists have examined the susceptibility of real clouds to this effect globally, for the first time. Their results help to validate predictions of the cloud albedo effect in climate models.

Aerosols – suspended particles of soot and other pollutants – affect the climate both directly and indirectly. They directly reflect or absorb solar radiation themselves. But their indirect effects on cloud properties may have a greater impact on global climate. One indirect aerosol effect, called the cloud albedo effect or the Twomey effect after the scientist who first described it, increases the amount of solar energy reflected from a cloud. It happens because aerosols act as cloud condensation nuclei, so clouds with added aerosols develop a greater number of smaller water droplets. Increasing the albedo (or diffuse reflectivity) of clouds in this way causes a cooling effect, or in other words, a negative radiative forcing.

While the cloud albedo effect is characterised in many global climate models, it is very challenging to measure directly. The physical properties of clouds are complex and constantly changing. Different types of cloud respond differently to aerosols and it is extremely hard to be sure whether an observed difference in albedo is caused by aerosols, by other factors such as temperature and humidity change, or by different initial cloud properties. Now, atmospheric physicists Lazaros Oreopoulos and Steve Platnick from the NASA Goddard Space Flight Centre, US, have taken a new approach to finding out how the albedo of the world's clouds can be expected to respond to added aerosols. They used cloud observations taken by MODIS (Moderate Resolution Imaging Spectroradiometer), an imaging system aboard two NASA Earth Observation satellites launched at the start of this century.

Data from MODIS provided global maps of actual cloud albedo for four months in 2005, calculated from measurements of each cloud’s opacity (known as optical thickness) and water droplet distribution. Oreopoulos and Platnick then superimposed a uniform change in the concentration of water droplets onto all the clouds and re-calculated their albedo. "Essentially, we mimic the effect of adding more aerosols," says Oreopoulos. Their results showed two general patterns. First, clouds over oceans are more sensitive to aerosol addition, increasing their reflectance more than those over land. "This is partly because of the properties of marine clouds before they were perturbed, and partly because they are sitting over a dark surface – the ocean," says Oreopoulos. The other pattern is that clouds at high latitudes are less sensitive to aerosols than those nearer the equator.

The study found that if you increase the number of water droplets in the clouds by 10%, it leads to a global change in radiative forcing of 1–2 Wm–2. Happily, this is similar to the numbers emerging from climate models that have not incorporated observational cloud data. The team now plans to collaborate with climate modellers and predict the effect of a more realistic, variable distribution of aerosols on their cloud data. They are also starting to investigate the potential effect of aerosols on ice clouds, which are far less well understood. "The data coming out of MODIS are relatively new, and there is still a lot of science we can do with them," says Platnick.

Source: http://environmentalresearchweb.org/cws/article/research/35349

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> http://www.geo-earth.com/forums/index.php?showtopic=7537

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Seals “Assist” in Climate Change Research

Mongabay.com – August 11, 2008

One area of the world that has been impossible to monitor is the sea-ice of Antarctica's Southern Ocean. The inability of satellites to 'see' through the ice and the difficulty for ships in exploring them has made these regions a blank zone for data collection related to climate change research. However group of researchers has found a way around these challenges. Ingeniously, they have attached oceanographic sensors to elephant seals that dive deep and feed among the sea ice.

The invaluable seals "provided a 30-fold increase in hydrographic profiles from the sea-ice zone," the researchers write. In addition they allow "the major fronts to be mapped south of 60°S and sea-ice formation rates to be inferred from changes in upper ocean salinity." The seals have the ability to dive 1500 meters and stay underwater for up to two hours. To study the data gaps, scientists tagged 58 elephant seals on four Antarctic islands. The seals swim distances of 35-65 kilometers (21-40 miles) in search of food, all the while taking important measurements of ocean salinity, temperature, and in some places sea-ice formation. Combing the conventional data provided by ships and satellites with the seal-collected information provide a far greater view of the Southern Ocean. "Elephant seals fill a ‘blind spot’ in our sampling coverage," the authors write, "enabling the establishment of a truly global ocean-observing system." The researchers suggest that the same usage of elephant seals for climate data should be extended to other Antarctic predators, including other seal species.

Read Full Article: http://news.mongabay.com/2008/0811-hance_seals.html



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> http://www.environmenthub.com/posts/3381/seals-assist-in-climate-change-research.aspx
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