Arctic News: air

Showing posts with label air. Show all posts

Sunday, August 19, 2018

Will August 2018 be the hottest month on record?

July and August are typically about 3.6ºC or 6.5ºF warmer than December and January. August is typically 1.8°C or 3.24ºF warmer than the average annual temperature. Above image shows how much higher the temperature was for selected months, compared to the annual global mean for the period 1980-2015. Will August 2018 be the hottest month on record?

Numerous temperature records have fallen across the world recently. Heat stress hazard is high under conditions of high surface air temperature and high relative humidity. When looking at heat stress hazards, it's therefore important to look at surface air temperatures over land, i.e. the temperature of the air above the land surface.

Fire hazard is high under conditions of hot and dry soil and strong wind. When looking at fire hazards, it's therefore important to look at land surface temperatures, reflecting how hot the surface of the Earth would feel to touch in a particular location. The map below shows land surface temperatures.

When calculating how much warmer it is now, a number of things must be taken into account:

Baseline

What baseline is used and how is the temperature at the baseline calculated? In the image at the top, the baseline is 1980-2015, which is a very recent period. When using a preindustrial baseline, anomalies could be more than 0.6°C higher than when using the 1951-1980 baseline that NASA normally uses.
Surface temperatures or surface air temperatures?

Above map shows land surface temperatures. As said above, this is different from surface air temperatures over land that show the temperature of the air above the land surface.

Similarly, sea surface temperatures indicate the temperature of the water at the surface. Sea surface air temperatures, on the other hand, are slightly higher, they are measurements of the air temperature just above the surface of the water.

NASA typically uses surface air temperatures over land, while using surface water temperatures over oceans. When instead using air temperatures globally, the temperature anomaly could be more than 0.1°C higher.
Missing data

How are missing data dealt with? To calculate the global mean on maps, NASA uses four zonal regions (90-24ºS, 24-0ºS, 0-24ºN, and 24-90ºN) and fills gaps in a region by the mean over the available data in that region. In datasets, however, missing data are typically ignored. This could make a difference of 0.2°C. Ignoring data for the Arctic alone could make a difference of 0.1°C.

Depending on how the above three points are dealt with, the temperature in August 2018 may well be more than 3°C above the mean annual global temperature in 1750. The question is whether August 2018 will be warmer than August 2016, which was 2.3°C warmer than 1980-2015.

Anthropogenic Global Warming

Remember the Paris Agreement, when politicians pledged to take efforts to ensure that the temperature would not cross 1.5°C above pre-industrial? Why did the Paris Agreement not specify a year for pre-industrial? Perhaps the idea was that total anthropogenic global warming should not exceed 1.5°C. In other words, the warming that people had already caused by 1750, plus the warming people caused since 1750, plus the warming that is already baked in for the decades to come. The image below illustrates this idea and also shows that we're well above 1.5°C anthropogenic global warming.

In the image below, temperatures have also been adjusted to better reflect a preindustrial baseline (1750), showing that temperatures were not higher than 1°C above pre-industrial during the entire Holocene, until recently.

In a recent paper, James Hansen et al. conclude that temperatures also weren't more than 1°C above pre-industrial during the previous interglacial, the Eemian, which implies that temperatures haven't been more than 1°C above pre-industrial for the entire 200,000 years that modern people, i.e. the species homo sapiens, have existed, and that temperatures have only recently rising to levels more than 1°C above pre-industrial. Quite likely, to find temperatures as high as today's, one would have to go back some 3 million years.

Fires over North America, August 2018

Fires can significantly influence temperatures in a number of ways. The images below show how fires boosted carbon dioxide, carbon monoxide and sulfur dioxide levels on August 19, 2018. Carbon dioxide and carbon monoxide both raise temperatures. On the other hand, sulfur dioxide lowers temperature by reflecting sunlight back into space.

Top left: carbon monoxide as high as 51495 ppb

Top right: carbon dioxide as high as 836 ppm

Bottom left: Smoke over North America

Bottom right: sulfur dioxide as high as 1917.57 µg/m³

The image below illustrates to what extent smoke from fires boosted black carbon in the air over North America on August 23, 2018. Black carbon causes both cooling and warming. Black carbon shades the surface, somewhat cooling the surface of land and water, while it also absorbs heat, thus warming the air above the surface. Furthermore, black carbon causes warming by darkening the surface once it settles down. Studies have calculated that black carbon has a total net global warming effect of more than 1.1 W/m².

Dust and further aerosols

The impact of aerosols such as sulfur dioxide and dust is often overlooked. The image below shows that τ, i.e. light at 550 nm as a measurement of aerosol optical thickness due to dust aerosols, was as high as 4.0641 on June 16, 2018.

[ goats, from Wikipedia ]

Dust is one reason why temperatures didn't cross the 1°C above pre-industrial mark during the peak of the recent Milankovitch cycle. A recent study calculates that the global annual mean surface temperature increases by 0.3°C for the mid-Holocene (6 ka), if the dust is completely removed.

Most dust appears to originate from the Sahara Desert, which lost its vegetation during the Holocene due to goats, according to this study, as people removed predators such as lions and tigers. As the Sahara lost its vegetation, the surface became more reflective, while dust further made that temperatures didn't rise as much as they otherwise would have.

Deforestation has caused a lot of carbon dioxide to be added during pre-industrial times, and there is also the impact of black carbon aerosols, resulting from biomass and fossil fuel burning, which causes some 1.1W/m² warming today and some 0.2W/m² is coming from pre-industrial activities.

In conclusion, temperatures would be a lot lower in the absence of human activities, while total anthropogenic global warming over the past few thousand years is much larger than most people think.

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

Links

• NASA - The Northwest is Running Hot and Dry
https://earthobservatory.nasa.gov/images/92601/the-northwest-is-running-hot-and-dry

• NASA GISS (Goddard Institute for Space Studies) Surface Temperature Analysis (GISTEMP)
https://data.giss.nasa.gov/gistemp

• NASA - Just Another Day on Aerosol Earth
https://earthobservatory.nasa.gov/images/92654/just-another-day-on-aerosol-earth

• Aerosols
https://arctic-news.blogspot.com/p/aerosols.html

• How much warming have humans caused?
https://arctic-news.blogspot.com/2016/05/how-much-warming-have-humans-caused.html

• How much warmer is it now?
https://arctic-news.blogspot.com/2018/04/how-much-warmer-is-it-now.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

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

Thursday, January 30, 2014

Forecast: America to be hit by temperatures as low as minus 40 degrees

The image on the right shows that large parts of North America, the Arctic Ocean and Siberia are experiencing low temperatures.

What many people may not realize is that temperatures in the Arctic are actually a lot higher than they used to be around this time of year.

Temperatures in the Arctic have risen due to feedbacks as described in the post The Biggest Story of 2013.

As a result, temperature anomalies above 20 degrees Celsius now feature in the Arctic. As the image on the right illustrates, the once-common temperature difference between the Arctic and lower latitudes has been shattered, and this is weakening the Jet Stream and the Polar Vortex, in turn making it easier for cold air to flow down to lower latitudes and for warmer air to enter the Arctic, as described in posts at this blog for years, e.g. this post.

This is illustrated by the image below, showing that the Arctic is hit by an overall temperature anomaly of 6.55 degrees Celsius, while some areas in the Arctic feature anomalies above 20 degrees Celsius.

Forecasts show that on February 2nd, 2014, 1200 UTC, the Arctic will be hit by a temperature anomaly of 7.85 degrees Celsius, while on February 6th, 2014, 1200 UTC, the U.S. will be hit by temperatures as low as -40 degrees, as illustrated by the image below.

The video below shows temperature forecasts from February 1to February 8, 2014.

The video below shows temperatire anomalies from February 2 to February 9, 2014.

Meanwhile, the Gulf Stream keeps pushing warm water into the Arctic Ocean, as illustrated by the image below.

Click on image to enlarge - view updated animation at earth.nullschool.net

The image below shows how high sea surface temperature anomalies stretch out from the point where the Gulf Stream travels at high speeds, off the coast of North America, all the way into the Arctic Ocean.

This has already resulted in methane eruptions from the seafloor of the Arctic Ocean that started several months ago and are continuing to date - ominous signs of more to come. The image below, which compares peak methane levels at two altitudes between January 2013 and January 2014, suggests that January 2014 peak levels have increased strongly, compared to January 2013 peak levels. Furthermore, that the rise in average peak readings has been most dramatic at the higher altitude.

This suggests that huge quantities of methane have indeed been released from hydrates under the Arctic ocean, and that much of the methane is rising and building up at higher altitudes. The increasing appearance of noctilucent clouds further confirms indications that methane concentrations are rising at higher altitudes.

Of course, the above analysis uses a limited dataset, but if verified by further analysis, it would confirm a dramatic rise in the presence of methane in the atmosphere due to releases from hydrates. Moreover, it would confirm the immensity of threat that releases from the Arctic Ocean will escalate and trigger runaway warming, as high methane concentrations over the Arctic are contributing to the anomalously high temperatures there. The risk that this will eventuate is unacceptable, which calls for comprehensive and effective action such as discussed at the ClimatePlan blog.

Huge patches of warm air over the Arctic

Over the past month or so, huge patches with temperature anomalies of over 20 degrees Celsius have been forming over the Arctic.

The three images below show such patches stretch out from Svalbard to Novaya Zemlya (top), north of Eastern Siberia (middle) and over West Greenland and Baffin Bay (bottom).

How these patches with warm air developed is further illustrated by the animation below, which goes from February 12, 2013, to March 18, 2013.

Amplification of climate change in the Arctic

In contrast to multi-year old ice, first-year old ice—ice that formed only since the last melt season—is thinner, saltier, and much more prone to melt.

Over the years, the loss of sea ice has become especially manifest in the older ice, as illustrated by the image below.

Salt content and hardness play a part in multi-year ice’s resistance to melt, explains a recent NOAA article, but the main characteristic that allows the ice to survive the melt season is thickness.

Screenshots from: PIOMAS Arctic Sea Ice Thickness Simulation 1978-2011

The decline in thickness over the years goes a long way to explain the self-reinforcing character of sea ice decline in the Arctic.

As another recent NOAA article describes, there is “something extra” behind the record ice retreats of the past 6 years: each June, the prevailing winds shifted from their normal west-to-east direction and instead blew strongly from the south across the Bering and Chuchki Seas (left on the image below), over the North Pole, and out toward Fram Strait. (The length of the lines is qualitative: longer lines mean stronger winds.)

Average June wind vectors in 2007-2012 (orange) compared to 1981-2010 average (white) based on NCEP reanalysis data provided by Physical Sciences Division at NOAA ESRL. Map by Dan Pisut, NOAA Environmental Visualization Lab.

The image below shows the unusual air pressure patterns that gave rise to the wind shift. Air pressure across the Arctic in Junes from 2007-2012 was completely lopsided, with two pockets of higher-than-average pressure sprawled across the North American Arctic and Greenland. These areas of high pressure act like boulders in a river. They slow and disrupt the normal westerly flow of the wind, forcing it to make, large, meandering detours to the north or south.

Average geopotential height anomaly at 700 millibar pressure level in Junes from 2007-2012 compared to the long-term average (1981-2010) based on NCEP reanalysis data provided by PSD at NOAA ESRL. Orange colors are higher-than-average pressure; blue is lower-than-average pressure. Map by Dan Pisut, NOAA Environmental Visualization Lab.

Arctic oceanographer and his NOAA colleagues think these “blocking highs” on the North American side of the Arctic created the unusually strong southerly flow that brought warm air into the central Arctic and over Greenland. The persistent southerly winds would help explain both the record low sea ice extent in summer 2012, as well as the island-wide melting of the surface of the Greenland Ice Sheet, which satellites detected in July 2012.

“This story started with us trying to figure out why the sea ice extents of the past 6 years or so have been so much lower than we would expect based on the long-term warming trend alone,” says Overland, “and we think this unusual circulation of the Arctic atmosphere is major part of it.”

Why, asks Overland, have these high pressure patterns have been forming so consistently each June for the past six years? The repeated appearance of these atmospheric features each June is so unusual that it’s the equivalent of a 1-in-a-1000 event. Can this be attributed to natural variability?

Instead, Overland’s hunch is that the cause is a change in the atmosphere that is itself connected to climate change in some way, possibly linked to record and near-record low June snow cover in the Canadian Arctic in recent years. “We don’t know that part of the story yet,” he says, “but this would certainly be the type of amplification of climate change [warming triggers changes that lead to more warming] we have been expecting to see in the Arctic.”

References

- Arctic Sea Ice Getting Thinner, Younger
http://www.climatewatch.noaa.gov/article/2012/arctic-sea-ice-getting-thinner-younger

- June wind shift a little something extra behind recent Arctic ice losses
http://www.climatewatch.noaa.gov/article/2012/june-wind-shift-a-little-something-extra-behind-recent-arctic-ice-losses

- Poles apart: A record-breaking summer and winter
http://nsidc.org/arcticseaicenews/2012/10/poles-apart-a-record-breaking-summer-and-winter/

- PIOMAS Arctic Sea Ice Thickness Simulation 1978-2011, published Sep 14, 2012 by ArctischePinguin