Arctic News: black carbon

Showing posts with label black carbon. Show all posts

Thursday, July 13, 2017

Wildfires

Levels of carbon dioxide (CO2) in the atmosphere are accelerating, even though emissions from fossil fuel burning have remained virtually the same over the past few years.

One of the reason behind this is accelerating emissions from wildfires as temperatures are rising.

Wildfires in Nevada caused CO2 to reach levels as high as 742 ppm on July 12, 2017 (green circle image on the right).

Global warming is greatly increasing the chance for what was previously seen as an extreme weather event to occur, such as a combination of droughts and storms. Heat waves and droughts can cause much vegetation to be in a bad condition, while high temperatures can come with strong winds, storms and lightning.

Wildfires cause a range of emissions, including CO2, soot, methane and carbon monoxide (CO). In Nevada, CO levels were as high as 30.43 ppm (green circle image right).

Above satellite image below shows the smoke plumes and the charred area. The google maps image below further shows where the fires were burning.

At the moment, wildfires are hitting many places around the world.

Wildfires caused carbon dioxide to reach levels as high as 746 ppm in Kazakhstan on July 11, 2017 (green circle on image on the right).

Carbon monoxide levels in the area were as high as 20.96 ppm on July 10, 2017.

The satellite image shows wildfires in Kazakhstan on July 9, 2017.

The satellite images show wildfires in Kazakhstan on July 11, 2017.

On July 16, 2017, CO₂ reached levels as high as 830 ppm in North America at the location marked by the green circle on the image below. Note that fires are burning at multiple locations.

The image below shows the location (red marker) where the fires burned in Canada.

That same day, July 16, 2017, CO₂ reached levels as high as 873 ppm in Mongolia, as shown by the image on the right.

The image also shows further fires burning in Siberia.

Carbon monoxide levels were as high as 37.19 ppm where the fires burned in Mongolia on July 16, 2017, as shown by the image below.

The image below shows the location (red marker) where the fires burned in Mongolia. The image also shows Lake Baikal across the border with Russia.

On July 22, 2017, CO₂ reached levels as high as 1229 ppm in Montana, while CO levels at the time were as high as 56.38 ppm at that location (green circle on image below).

The satellite image below shows the situation in Montana on the next day, July 23, 2017. See also the
NASA post Grassland Fires Tear Through Montana.

Furthermore, on July 23, 2017, CO₂ reached levels as high as 884 ppm at another (nearby) location in Montana (green circle on image below).

Meanwhile, temperatures keep rising. Surface temperature as high as 53.1°C or 127.5°F were forecast in Iran for July 11, 2017, at the location marked by the green circle on the image below.

At 1000 mb (image below), temperatures in Iran were forecast to be slightly lower, i.e. as high as 51.9°C or 125.3°F at the location marked by the at green circle, but note the difference in color, especially over Greenland, the Himalayas and the Tibetan Plateau.

The situation is dire and calls for comprehensive and effective action as described at the Climate Plan.

Aerosols

Some aerosols, particularly sulfur dioxide, have a cooling effect, making that they partly mask the warming effect of other emissions by people. The IPCC AR4 image below shows that the direct and cloud albedo effect of aerosols equals a radiative forcing of as much as -2.7 W/m². In other words, if this masking effect were to fall away, warming would increase by as much as 2.7 W/m², according to IPCC AR4 figures.

Anthropogenic aerosols are also suppressing the Pacific Decadal Oscillation, making that less heat gets transferred from oceans to the atmosphere. Recent research concludes that future reduction of anthropogenic aerosol emissions, particularly from China, would promote positive Pacific Decadal Oscillation, thus further speeding up warming over the coming years.

Dimethyl sulphide emissions from oceans constitute the largest natural source of atmospheric sulphur, and such emissions can decrease with ongoing ocean acidification and climate change. This could particularly impact specific regions such as Antarctica, speeding up warming and loss of sea ice there, as discussed at this paper.

The net warming effect of open biomass burning was estimated in a 2014 study by Mark Jacobson to amount to 0.4 W/m² of radiative forcing. Imagine a scenario in which many people stopped burning fossil fuels for heating, cooking and energy. That would be great, but if many of them instead switched to burning biomass in woodburners and open fires, while wildfires increased strongly, the net warming from associated aerosols would increase dramatically.

A recent paper by James Hansen uses equilibrium fast-feedback climate sensitivity of ¾°C per W/m², while another recent paper suggest that the temperature rise per W/m² could be even stronger.

A high-end increase in net radiative forcing combined with a strong temperature rise per W/m² could cause a temperature rise as a result of changes in aerosols of as much as 2.5°C in a matter of years, as suggested in earlier posts such as this one.

Thursday, June 25, 2015

Accelerated Warming in the Arctic

Warming in the Arctic is accelerating. On June 25, 2015, high temperatures hit North America. Temperatures as high as 30.3°C (86.54°F) were recorded where the Mackenzie River is flowing into the Arctic Ocean.

June 25, 2015 - High temperatures over North America, close to the Arctic Ocean

On July 1, 2015, temperatures are forecast to be as high as 111.4°F (or 44.1°C) near Chico, north of San Francisco. Temperatures are forecast to be high over most of North America and Eastern Siberia, threatening to further warm up waters of the Arctic Ocean.

Forecast for July 1, 2015 - High temperatures over North America, close to the Arctic Ocean

The image below shows that on June 27, 2015, temperatures of well over 40°C (104°F) were recorded in Europe and in Pakistan, where temperatures earlier this month had reached 49°C (120.2°F) in some places. The heat wave reportedly killed 1233 people in Karachi alone. This in addition to the 2500 people killed earlier in India by high temperatures.

June 27, 2015 - High temperatures over Russia, close to the Arctic Ocean

High temperatures at such locations are very worrying, for a number of reasons, including:

They are examples of heatwaves that can increasingly extend far to the north, all the way into the Arctic Ocean, speeding up warming of the Arctic Ocean seabed and threatening to unleash huge methane eruptions.
They set the scene for wildfires that emit not only greenhouse gases such as carbon dioxide and methane, but also pollutants such as carbon monoxide (that depletes hydroxyl that could otherwise break down methane) and black carbon (that when settling on ice causes it to absorb more sunlight).
They cause warming of the water of rivers that end up in the Arctic Ocean, thus resulting in additional sea ice decline and warming of the Arctic Ocean seabed.

June 24, 2015 - Smoke from wildfires in Alaska - from: wunderground.com

The image below shows increased sea surface temperature anomalies in the Arctic. Note the warming in the area of the Beaufort Sea where the Mackenzie River is flowing into the Arctic Ocean.

Very warm water is also flowing from the Pacific Ocean through the Bering Strait into the Arctic Ocean. As the image below shows, the water that is flowing into the Arctic Ocean from the Pacific is much warmer than it used to be, as much as 6.1°C (10.98°F) warmer.

View the flow of the water on the animated version of above image at earth.nullschool.net

As said above, warm water flowing from rivers into the Arctic Ocean is a major contributor to these sea surface temperature anomalies. As also illustrated by the NOAA image below, rivers carrying warm water into the Bering Strait include the Kobuk River, the Naotak River and the Yukon River that flows all the way from British Columbia, Canada, through Alaska and ends in the Bering Strait. Sea surface temperatures near the coast of Alaska were as high as 19°C (66.2°F) from June 21-24, 2015.

Sea surface temperatures near the coast of Alaska as high as 19°C (66.2°F) from June 21-24, 2015

The Naval Research Laboratory animation below shows changes to Arctic sea ice thickness. Sea ice thickness (in m) down to zero where the Mackenzie River flows into the Arctic Ocean and in the Bering Strait where warm water from the Pacific is entering the Arctic Ocean.

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan.

Related

- Gulf Stream brings ever warmer water into Arctic Ocean
http://arctic-news.blogspot.com/2015/06/gulf-stream-brings-ever-warmer-water-into-arctic-ocean.html

- High Temperatures in the Arctic

http://arctic-news.blogspot.com/2015/06/high-temperatures-in-the-arctic.html

- Heat Wave Forecast For Russia Early June 2015http://arctic-news.blogspot.com/2015/06/heat-wave-forecast-for-russia-early-june-2015.html

Sea surface temperature anomalies in the Arctic. Note the warming in the area of the Beaufort Sea where the Mackenzie...
Posted by Sam Carana on Thursday, June 25, 2015

Friday, July 18, 2014

Smoke Blankets North America

A thick layer of smoke blankets large parts of North America, as also illustrated by the animation below based on images from July 15 to 18, 2014, from Wunderground.com.

[ note that this animation is a 2.3MB file that may take some time to fully load ]

The are also extensive wildfires throughout the boreal forest and tundra zones of Central Siberia in Russia.

Such wildfires can send huge amounts of carbon dioxide, methane, soot, dust and volatile organic compounds into the atmosphere. Much of this gets deposited at higher latitudes, discoloring land, snow and ice, and thus speeding up warming by absorbing more sunlight that was previously reflected back into space.

Soils at higher latitudes can contain huge amounts of carbon in the form of peat, as described in the earlier post The Threat of Wildfires in the North. There are further conditions that make the situation in the Arctic so dangerous.

Temperature anomaly March-April-May-June 2014 (JMA)

The Arctic is particularly vulnerable to warming due to geographics. Seas in the Arctic Ocean are often shallow and covered by sea ice that is disappearing rapidly. Largely surrounded by land that is also rapidly losing its snow and ice cover, the Arctic Ocean acts like a trap capturing heat carried in by the Gulf Stream, which brings in ever warmer water. Of all the heat trapped on Earth by greenhouse gases, 90% goes into oceans, while a large part of the remaining 10% goes into melting the snow and ice cover in the Arctic, as described in an earlier post. Such basic conditions make that the Arctic is prone to warming.

Then, there are huge amounts of methane held in sediments under the Arctic Ocean, in the form of hydrates and free gas. Unlike methane releases from biological sources elsewhere on Earth, methane can be released from the seafloor of the Arctic Ocean in large quantities, in sudden eruptions that are concentrated in one area.

Until now, permafrost and the sea ice have acted as a seal, preventing heat from penetrating these methane hydrates and causing further destabilization. As long as there is ice, additional energy will go into melting the ice, and temperatures will not rise. The ice also acts as a glue, keeping the soil together and preventing hydrate destabilization from pressure changes and shockwaves resulting from seismic activity. Once the ice is gone, sediments become prone to destabilization and heat can more easily move down along fractures in the sediment, reaching hydrates that had until then remained stable.

Temperature anomaly March-April-May 2014 (NASA)

When methane escapes from the seafloor of the Arctic Ocean and travels through waters that are only shallow, there is little opportunity for this methane to be broken down in the water, so a lot of it will enter the atmosphere over the Arctic Ocean. The Coriolis effect will spread the methane sideways, but latitudes over the Arctic are relatively short, making the methane return at the same spot relatively quickly, while the polar jet stream acts as a barrier keeping much of the methane within the Arctic atmosphere. In case of large methane eruptions, the atmosphere over the Arctic will quickly become supersaturated with methane that has a huge initial local warming potential.

Hydroxyl levels in the atmosphere over the Arctic are very low, extending the lifetime of methane and other precursors of stratospheric ozone and water vapor, each of which have a strong short-term local warming potential. In June/July, insolation in the Arctic is higher than anywhere else on Earth, with the potential to quickly warm up shallow waters, making that heat can penetrate deep into sediments under the seafloor.

created by Sam Carana, part of AGU 2011 poster

The initial impact of this methane will be felt most severely in the Arctic itself, given the concentrated and abrupt nature of such releases, with the danger that even relatively small releases of methane from the seafloor of the Arctic can trigger further destabilization of hydrates and further methane releases, escalating into runaway warming.

This danger is depicted in the image on the right, showing how albedo changes and methane releases act as feedbacks that further accelerate warming in the Arctic, eventually spiraling into runaway global warming.

The currently very high sea surface temperature anomalies are illustrated by the two images below.

As the image below right shows, sea surface temperatures as high as 18 degrees Celsius (64.4 degrees Fahrenheit) are currently recorded in the Arctic.

Albedo changes and methane releases are only two out of numerous feedbacks that are accelerating warming in the Arctic.

Also included must be the fact that Earth is in a state of energy imbalance. Earth is receiving more heat from sunlight than it is emitting back into space. Over the past 50 years, the oceans have absorbed about 90% of the total heat added to the climate system, while the rest goes to melting sea and land ice, warming the land surface and warming and moistening the atmosphere.

In a 2005 paper, James Hansen et al. estimated that it would take 25 to 50 years for Earth’s surface temperature to reach 60% of its equilibrium response, in case there would be no further change of atmospheric composition. The authors added that the delay could be as short as ten years.

Earth's waters act as a buffer, delaying the rise in land surface temperatures that would otherwise occur, but this delay could be shortened. Much of that extra ocean heat may enter the atmosphere much sooner, e.g. as part of an El Niño event. Another buffer, Arctic sea ice, could collapse within years, as illustrated by the image below.

[ click on image to enlarge ]

The demise of sea ice comes with huge albedo changes, resulting in more heat getting absorbed by the Arctic Ocean, in turn speeding up warming of the often shallow waters of the Arctic Ocean. This threatens to make heat penetrate subsea sediments containing huge amounts of methane. Abrupt release of large amounts of methane would warm up the Arctic even more, triggering even further methane releases in a spiral of runaway warming.

Particularly worrying is the currently very warm water that is penetrating the Arctic Ocean from the Atlantic Ocean and also from the Pacific Ocean, as illustrated by the image further above and the image on the right.

The danger is that the Arctic will warm rapidly with decline of the snow and ice cover that until now has acted as a buffer absorbing heat, with more sunlight gets absorbed due to albedo changes and as with additional emissions, particularly methane, resulting from accelerating warming in the Arctic.

The numerous feedbacks that accelerate warming in the Arctic are pictured in the image below.

[ from: climateplan.blogspot.com/p/feedbacks.html ]

Furthermore, the necessary shift to clean energy will also remove the current masking effect of aerosols emitted when burning fuel. One study finds that a 35% – 80% cut in people's emission of aerosols and their precursors will result in about 1°C of additional global warming.

In the video below and the video further down below, Guy McPherson discusses Climate Change and Human Extinction.

from: http://fossilfreeri.org/2014/07/13/guy-mcphersons-climate-change-the-end-part-4/

This is further illustrated by the image below, showing how surface temperature rises are accelerating in the Arctic compared to global rises, with trendlines added including one for runaway global warming, from How many deaths could result from failure to act on climate change?

[ click on image to enlarge ]

The situation is dire and calls for comprehensive and effective action, as discussed at the Climate Plan blog.

Hat tip to Jim Kirkcaldy for pointing at the wildfire development at an early stage.

Post by Sam Carana.

Wednesday, July 10, 2013

Wildfires even more damaging

Wildfires cause even more damage than many climate models assume. Much has been written about the threat that wildfires pose to people's safety and health, to crop yields, and the quality of soils and forests.

In addition, wildfires pose a huge threat in terms of climate change, not only due to the impact of emissions on the atmosphere, but there's also the impact of particles (soot, dust and volatile organic compounds) settling down on snow and ice, speeding up their demise through albedo changes. This contributes to the rapid decline of the sea ice and snow cover in the Arctic, a decline that has been hugely underestimated in many climate models.

Furthermore, global warming and accelerated warming in the Arctic cause extreme weather conditions in many places, an impact that is again underestimated in many climate models.

A team of scientists from Los Alamos and Michigan Technological University, led by Swarup China, points out that continued global warming will make conditions for wildfires worse, as was already noted in earlier studies, such as this 2006 study. They also point at the conclusion of a recent study that more biomass burning will lead to more ozone, less OH, and a nonlinear increase of methane's lifetime.

Mixing and classification of soot particles. Field-emission
scanning electron microscope images of four different
categories of soot particles: (a) embedded, (b) partly coated,
(c) bare and (d) with inclusions. Approximately 50% of the
ambient soot particles are embedded, 34% are partly coated
and 12% have inclusions. Only 4% of the particles are bare
soot (not coated or very thinly coated). Scale bars, 500 nm.
Right, spherical tar balls dominate in the emissions.

The scientists recently completed an analysis of particles from the Las Conchas fire that started June 26, 2011, and was the largest fire in New Mexico's history at the time, burning 245 square miles. One of the scientists, Manvendra Dubey, said:

“Most climate assessment models treat fire emissions as a mixture of pure soot and organic carbon aerosols that offset the respective warming and cooling effects of one another on climate. However Las Conchas results show that tar balls exceed soot by a factor of 10 and the soot gets coated by organics in fire emissions, each resulting in more of a warming effect than is currently assumed.”

“Tar balls can absorb sunlight at shorter blue and ultraviolet wavelengths (also called brown carbon due to the color) and can cause substantial warming,” he said. “Furthermore, organic coatings on soot act like lenses that focus sunlight, amplifying the absorption and warming by soot by a factor of 2 or more. This has a huge impact on how they should be treated in computer models.”

Finally, many climate models ignore the threat of large, abrupt methane releases in the Arctic. As discussed in many earlier posts at Arctic-news blog, accelerated warming in the Arctic threatens to spiral out of control as methane levels rise over the Arctic, causing destabilization of methane hydrates and further methane releases, escalating into runaway global warming.

Wednesday, January 2, 2013

Turning forest waste into biochar

Too much biomass waste in tundra and boreal forests makes them prone to wildfires, especially when heatwaves strike. Furthermore, leaving biomass waste in the forest can cause a lot of methane emisions from decomposition.

In order to reduce such methane emissions and the risk of wildfires, it makes sense to reduce excess biomass waste in fields and forests. Until now, this was typically done by controlled burning of biomass, which also causes emissions, but far less than wildfires do. Avoiding wildfires is particularly important for the Arctic, which is vulnerable to soot deposits originating from wildfires in tundra and boreal forest. Such soot deposits cause more sunlight to be absorbed, accelerating the decline of snow and ice in the Arctic.

A team of scientists at University of Washington, sponsored by the National Science Foundation, has developed a way to remove woody biomass waste from forests without burning it in the traditional way. The team has developed a portable kiln that can be assembled around a heap of waste wood and convert it to biochar on the spot, while the biochar can also be burried in the soil on the spot.

Demonstration in Kerby, Oregon,
Nov. 6, 2012, by Carbon Cultures.
Credit: Marcus Kauffman at Flickr

The team initially started testing the effectiveness of a heat-resistant blanket thrown over woody debris. The team then developed portable panels that are assembled in a kiln around a slash pile.

Students have set up a company, Carbon Cultures, to promote the technology and to sell biochar. CEO of Carbon Cultures is Jenny Knoth, also a Ph.D. candidate in environmental and forest sciences.

The kiln restricts the amount of oxygen that can reach the biomass, which is transformed by pyrolysis into biochar. The woody waste is heated up to temperatures of about 1,100 degrees Fahrenheit (600 Celsius), as the kiln transforms some 800 pounds of wood into 200 pounds of biochar in less than two hours. “We also extinguish with water because it helps keep oxygen out and also activates the charcoal [making it more fertile in soil].”

Currently, the total costs of disposing of forest slash heaps (the collections of wood waste) approximate a billion dollars a year in the United States, according to Knoth.

And of course, adding biochar to the soil is a great way to reduce carbon dioxide levels in the atmosphere. “Biochar is proven to fix carbon for hundreds of thousands of years,” Knoth said.

Demonstration in Kerby, Oregon, November 6, 2012, organized by Carbon Cultures. Credit: Marcus Kauffman at Flickr

As said, when biomass waste is left in the open air, methane emissions are produced during its decomposition. Moreover, such waste will fuel wildfires, which produce huge amounts of emissions. The traditional response therefore is to burn such waste. Pyrolyzing biomass produces even less greenhouse gases and less soot, compared to such controlled burning.

Biochar is produced in the process, which can be added to the soil on the spot. This will help soil retain moisture, nutrients and soil microbes, making forests more healthy, preventing erosion and thus reduces the risk of wildfires even further, in addition to the reduction already achieved by removal of surplus waste.

A healthy forest will retain more moist in its soil, in the air under its canopy, and in the air above the forest through expiration, resulting in more clouds that act as sunshades to keep the forest cool and return the moist to the forest through rainfall. Forests reinforce patterns of air pressure and humidity that result in long-distance air currents that bring moist air from the sea inland to be deposited onto the forest in the form of rain. Finally, clouds can reflect more sunlight back into space, thus reducing the chance of heatwaves.

References

- Recycling wood waste - The Daily of the University of Washington
- Helping Landowners with Waste Wood While Improving Agribusiness and Energy - National Science Foundation

Related

- Biochar
- CU-Boulder gets into biochar

- Fires are raging again across Russia
- Abrupt Local Warming

Saturday, December 1, 2012

Aviation Policies

The European Union's policy on Aviation Emissions

From the start of 2012, the European Union (EU) required its members to include emissions from flights arriving at and departing from their airports in the EU scheme of emissions allowances and trading, while encouraging other nations to take equivalent measures. The EU exempts biofuel and claims to take a 'comprehensive approach' to reducing environmental impacts of aviation. To create space for political negotiations to get an international agreement regulating emissions from aviation, the EU has meanwhile postponed implementation of its directive by one year.

What kind of international agreement could be reached on aviation emissions? What policies work best? How do aviation policies fit into a comprehensive approach?

A Comprehensive Plan of Action on Climate Change

A comprehensive plan is best endorsed globally, e.g. through an international agreement building on the Kyoto Protocol and the Montreal Accord. At the same time, the specific policies are best decided and implemented locally, e.g. by insisting that each nation reduces specific emissions by a set annual percentage, and additionally removes a set annual amount of carbon dioxide from the atmosphere and the oceans, followed by sequestration, proportionally to its current emissions.

Policy goals are most effectively achieved when policies are implemented locally and independently, with separate policies each addressing the specific shifts that are each needed to reach agreed targets. Each nation can work out what policies best fit their circumstances, as long as they each independently achieve agreed targets. Counting emissions where they occur will encourage nations to adopt effective policies, such as imposing fees on the sales of products in proportion to the emissions they cause, and adopting product standards that ban products that would otherwise cause unacceptably high emissions while clean alternatives are readily available.

Clean Energy Policies

Policies aiming to achieve a shift to clean energy will apply to many sectors such as transportation (including aviation), power plants, and industry and buildings which are also large consumers of fossil fuel. The above image also shows policies specifically targeting aviation, in addition to clean energy policies that apply across sectors.

The image below proposes feebates as the most effective way to accomplish the necessary shift to clean energy. In such feebates, fees are imposed on polluting energy and associated facilities, with revenues used - preferably locally - to fund rebates on clean energy and associated facilities.

In line with such feebates, each nation could impose fees on jetfuel, while using the revenues for a variety of purposes, preferably local clean energy programs. Where an airplane lands arriving from a nation that has failed to add sufficient fees, the nation where the airplane lands could impose supplementary fees. Such supplementary fees should be allowed under international trade rules, specifically if revenues are used to fund direct air capture of carbon dioxide.

Aviation Policies

As said, apart from clean energy policies, it makes sense to additionally implement policies specifically targeting aviation. Airplanes not only cause carbon dioxide emissions, but also cause other emissions such as black carbon and NOx, contrails and cirrus cloud effects. The EU emissions scheme only targets a limited set of emissions, while also looking at their global warming potential, rather than the potential of emissions to cause warming locally, specifically in the Arctic. A joint 2011 UNEP/WMO report mentioned many measures to reduce black carbon and tropospheric ozone, adding that their implementation could reduce warming in the Arctic in the next 30 years by about two-thirds.

A 2012 study by Jacobson et al. concludes that cross-polar flights by international aviation is the most abundant direct source of black carbon and other climate-relevant pollutants over the Arctic. Rerouting cross-polar flights to instead circumnavigate the Arctic Circle therefore makes sense. While such rerouting consumes more fuel, it could reduce fuel use and emissions within the Arctic Circle by 83% and delay pollutant transport to the Arctic.

Given the need to act on warming in the Arctic, it makes sense to ban cross-polar flights. To further reduce the flow of pollutants to the Arctic caused by aviation, it makes sense to add fees on all jet flights. Such fees on jet flights would be additional to the above fees on fuel. This could further facilitate a shift from aviation toward cleaner forms of transportation, such as high speed rail. Where the revenues of such fees are used to fund direct air capture, they could also help kickstart an industry that could produce synthetic jetfuel and that could be instrumental in bringing atmospheric levels of carbon dioxide back to 280ppm.

Tuesday, July 24, 2012

Greenland is melting at incredible rate

The combination-image below shows how much the ice on Greenland melted between July 8 (left) and July 12 (right).

On July 8, about 40% of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and some 97% of the ice sheet surface had thawed by July 12.

In the image, the areas classified as “probable melt” (light pink) correspond to those sites where at least one satellite detected surface melting. The areas classified as “melt” (dark pink) correspond to sites where two or three satellites detected surface melting. The satellites are measuring different physical properties at different scales and are passing over Greenland at different times. Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory.

For several days this month, Greenland's surface ice cover melted over a larger area than at any time in more than 30 years of satellite observations. Nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its two-mile-thick center, experienced some degree of melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists.

On average in the summer, about half of the surface of Greenland's ice sheet naturally melts. At high elevations, most of that melt water quickly refreezes in place. Near the coast, some of the melt water is retained by the ice sheet and the rest is lost to the ocean. But this year the extent of ice melting at or near the surface jumped dramatically. According to satellite data, an estimated 97% of the ice sheet surface thawed at some point in mid-July.

This extreme melt event coincided with an unusually strong ridge of warm air, or a heat dome, over Greenland. The ridge was one of a series that has dominated Greenland's weather since the end of May. "Each successive ridge has been stronger than the previous one," said Mote. This latest heat dome started to move over Greenland on July 8, and then parked itself over the ice sheet about three days later. By July 16, it had begun to dissipate.

As the ice warms, it loses albedo, i.e. less sunlight is reflected back into space. Darker surface absorbs more sunlight, accelerating the melting. The image below shows the Greenland ice sheet albedo from 2000 to 2011.

Credit: NOAA Arctic Report Card 2011.

The image below, from the meltfactor blog and by Jason Box and David Decker, shows the steep fall in reflectivity for altitudes up to 3200 meters in July 2012.

The image below, from the meltfactor blog, shows how the year 2012 compares with the situation at approximately the same time in previous years, 2011 and 2010, which are recognized as being record melt years.

The photo below shows how dark the ice sheet surface can become.

Photo shot by Jason Box on August 12, 2005

Loss of albedo occurs as the darker bare ground becomes visible where the ice has melted away. Darkening of snow and ice can start even before melting takes place. Warming changes the shape and size of the ice crystals in the snowpack, as described at this NASA Earth Observatory page. As temperatures rise, snow grains clump together and reflect less light than the many-faceted, smaller crystals. Additional heat rounds the sharp edges of the crystals, and round particles absorb more sunlight than jagged ones.

Dirty ice surrounds a meltwater stream near the margin of the ice sheet. Compared to fresh snow and clean ice, the dark surface absorbs more sunlight, accelerating melting. © Henrik Egede Lassen/Alpha Film, from the Snow, Water, Ice, and Permafrost in the Arctic report from the U.N. Arctic Monitoring and Assessment Programme. From NOAA Climatewatch.

Another factor contributing to darkening is aerosols, in particular soot (i.e. black carbon) from fires and combustion of fuel, dust and organic compounds that enter the atmosphere and that can travel over long distances and settle on ice and snow in the Arctic.

The July data since 2000, from the meltfactor blog, suggest a exponential fall in reflectivity that, when projected into the future (red line, added by Sam Carana), looks set to go into freefall next year.

Is a similar thing happening all over the Arctic? Well, the map below, edited from a recent SSMIS Sea Ice Map, shows that sea ice concentration is highest around the North Pole.

So, can water be expected to show up at the North Pole? Well have a look at the photo from the North Pole webcam below.

Photo from the North Pole webcam

It does look like melting is going on at the North Pole. Water is significantly darker than ice, meaning the overall reflectivity will be substantially lowered by this water.

It's important to realize that surface albedo change is just one out of a number of feedbacks, each of which deserves a closer look.

As shown on the image below, the IPCC describes four types of feedbacks with a joint Radiative Forcing of about 2 W/sq m, i.e. water vapor, cloud, surface albedo and lapse rate.

The image below, from James Hansen et al., may at first glance give the impression that all aerosols have a cooling effect.

When components are split out further, it becomes clear though that some aerosols are reflective and have a cooling effect, whereas black carbon has a warming effect, while changes in snow albedo also contribute to warming. On the interactive graph below, you can click on or hover over each component to view their radiative forcing. When isolated from other factors, it's clear that snow albedo has an increasing warming effect.
How much could Earth warm up due to decline of snow and ice? Professor Peter Wadhams estimates that the drop in albedo in case of total loss of Arctic sea ice would be a 1.3 W/sq m rise in radiative forcing globally, while additional decline of ice and snow on land could push the the combined impact well over 2 W/sq m.

Locally, the impact could be even more dramatic. The image below, from Flanner et al., shows how much the snow and ice is cooling the Arctic.

Image, edited by Sam Carana, from Mark Flanner et al. (2011).

Conversely, above image shows how much the Arctic could warm up without the snow and ice. Due to albedo change, sunlight that was previously reflected back into space will instead warm up the Arctic. What could have a big impact locally is that, where there's no more sea ice left, all the heat that previously went into melting will raise temperatures instead, as described at Warming in the Arctic.

The big danger is methane. Drew Shindell et al. show in Improved Attribution of Climate Forcing to Emissions that inclusion of aerosol responses will give methane a much higher global warming potential (GWP) than the IPCC gave methane in AR4, adding that methane's GWP would likely be further increased by including ecosystem responses. Indeed, as pictured in the image below, accelerated warming in the Arctic could trigger methane releases which could cause further methane releases, escalating into runaway global warming.