Showing posts with label Drew Shindell. Show all posts
Showing posts with label Drew Shindell. Show all posts

Sunday, January 20, 2019

Care for the Ozone Layer


The stratosphere normally is cold and very dry. Global warming can increase water vapor in the stratosphere in a number of ways. Global warming causes the troposphere to warm and since warmer air holds more water vapor, the amount of water vapor in the troposphere is increasing. This can cause more water vapor to end up in the stratosphere as well, as described below.

Stratospheric Water Vapor over the Arctic

Around the time of the December Solstice, very little sunlight is reaching the Arctic and temperatures over land at higher latitudes can get very low. At the same time, global warming has made oceans warmer and this keeps air temperatures over water relatively warm in Winter. This can lead to a number of phenomena including sudden stratospheric warming and moistening of the stratosphere.

Sudden stratospheric warming is illustrated by the image on the right, showing temperatures in the stratosphere over Siberia as high as 12.7°C or 54.9°F on December 24, 2018, and temperatures as low as -84.8°C or -120.6°F over Greenland.

At the same time, relative humidity was as high as 100% in the stratosphere over the North Sea, as the second image on the right shows.

Moistening of the stratosphere was even more pronounced on December 24, 2016, as illustrated by the third image on the right.

Storms over the U.S.

Jennifer Francis has long pointed out that, as temperatures at the North Pole are rising faster than at the Equator, the Jet Stream is becoming wavier and can get stuck in a 'blocking pattern' for days, increasing the duration and intensity of extreme weather events.

This can result in stronger storms moving more water vapor inland over the U.S., and such storms can cause large amounts of water vapor to rise high up in the sky.

Water vapor reaching stratospheric altitudes causes loss of ozone, as James Anderson describes in a 2017 paper and discusses in the short 2016 video below.


Methane

Stratospheric water vapor can also result from methane oxidation in the stratosphere. Methane concentrations have risen strongly at higher altitudes over the years. Noctilucent clouds indicate that methane has led to water vapor in the upper atmosphere.

The danger is that, as the Arctic Ocean keeps warming, large eruptions of methane will occur from the seafloor. Ominously, high methane levels have recently shown up on satellite images over the Arctic at lower altitudes, indicating the methane is escaping from the sea.

The images below show methane levels recorded by the NPP satellite:
Jan. 6, 2019, with peak levels of 2513 ppb at 1000 mb, 2600 ppb at 840 mb and 2618 ppb at 695 mb;
Jan. 11, 2019, with peak levels of 2577 ppb at 1000 mb, 2744 ppb at 840 mb and 2912 ppb at 695 mb;
Jan. 15, 2019, with peak levels of 2524 ppb at 1000 mb, 2697 ppb at 840 mb and 2847 ppb at 695 mb.

















The images below show methane levels recorded by the MetOp satellites:
Jan. 15, 2019, with peak levels of 2177 ppb at 840 mb, 2342 ppb at 695 mb and 2541 ppb at 586 mb;
Jan. 16, 2019, with peak levels of 2219 ppb at 840 mb, 2299 ppb at 695 mb and 2475 ppb at 586 mb;
Jan. 19, 2019, with peak levels of 2201 ppb at 840 mb, 2489 ppb at 695 mb and 2813 ppb at 586 mb.
















The Importance of the Ozone Layer

Increases in stratospheric water vapor are bad news, as they speed up global warming and lead to loss of stratospheric ozone, as Drew Shindell pointed out back in 2001.

It has long been known that deterioration of the ozone shield increases ultraviolet-B irradiation, in turn causing skin cancer. Recent research suggest that, millions of years ago, it could also have led to loss of fertility and consequent extinction in plants and animals (see box right).

Nitrous oxide

As the left panel of the image below shows, growth in the levels of chlorofluorocarbons (CFCs) has slowed over the years, but their impact will continue for a long time, given their long atmospheric lifetime (55 years for CFC-11 and 140 years for CFC-12, CCl2F2).

Furthermore, as the right panel shows, the impact of nitrous oxide (N₂O) as an ozone depleting substance (ODS) has relatively grown, while N₂O levels also continue to increase in the atmosphere.

[ click on images to enlarge ]
Existential Threats

In conclusion, rising levels of emissions by people constitute existential threats in many ways. Rising temperatures cause heat stress and infertility, and there are domino effects. Furthermore, stratospheric ozone loss causes cancer and infertility.

Only once the ozone layer formed on Earth some 600 million years ago could multicellular life develop and survive. Further loss of stratospheric ozone could be the fastest path to extinction for humanity, making care for the ozone layer imperative.

As described in an earlier post, Earth is on the edge of runaway warming and in a moist-greenhouse scenario oceans evaporate into the stratosphere with loss of the ozone layer.

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


Links

• Climate and ozone response to increased stratospheric water vapor, by Drew Shindell (2001)
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999GL011197

• Stratospheric ozone over the United States in summer linked to observations of convection and temperature via chlorine and bromine catalysis, by James Anderson et al. (2017)
https://www.pnas.org/content/114/25/E4905

• Harvard Speaks on Climate Change: James Anderson (2016)
https://vimeo.com/185794598

• Climate Week: Climate Science Breakfast with James Anderson (April 9, 2015)
http://environment.harvard.edu/climate-week-climate-science-breakfast-james-anderson

• 10°C or 18°F warmer by 2021?
https://arctic-news.blogspot.com/2017/04/10c-or-18f-warmer-by-2021.html

• Noctilucent clouds indicate more methane in upper atmosphere
https://arctic-news.blogspot.com/2012/09/noctilucent-clouds-indicate-more-methane-in-upper-atmosphere.html

• Noctilucent clouds: further confirmation of large methane releases
https://methane-hydrates.blogspot.com/2013/12/noctilucent-clouds-further-confirmation-of-large-methane-releases.html

• It could be unbearably hot in many places within a few years time
https://arctic-news.blogspot.com/2016/07/it-could-be-unbearably-hot-in-many-places-within-a-few-years-time.html

• Climate change: effect on sperm could hold key to species extinction, by Kris Sales
https://theconversation.com/climate-change-effect-on-sperm-could-hold-key-to-species-extinction-107375

• Climate change: effect on sperm could hold key to species extinction
https://theconversation.com/climate-change-effect-on-sperm-could-hold-key-to-species-extinction-107375

• UV-B–induced forest sterility: Implications of ozone shield failure in Earth’s largest extinction, by Jeffrey Benca et al. (2018)
http://advances.sciencemag.org/content/4/2/e1700618

• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
https://www.nature.com/articles/s41598-018-35068-1

• NOAA's Annual Greenhouse Gas Index
https://www.esrl.noaa.gov/gmd/aggi

• NOAA Study Shows Nitrous Oxide Now Top Ozone-Depleting Emission
https://www.esrl.noaa.gov/news/2009/nitrous_oxide_top_ozone_depleting_gas.html

• Earth is on the edge of runaway warming
https://arctic-news.blogspot.com/2013/04/earth-is-on-the-edge-of-runaway-warming.html

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html



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