UV exposure has increased over the last 30 years, but stabilized since the mid-1990s
From NASA Goddard press release here
NASA scientists analyzing 30 years of satellite data have found that the amount of ultraviolet (UV) radiation reaching Earth’s surface has increased markedly over the last three decades. Most of the increase has occurred in the mid-and-high latitudes, and there’s been little or no increase in tropical regions.
The new analysis shows, for example, that at one line of latitude — 32.5 degrees — a line that runs through central Texas in the northern hemisphere and the country of Uruguay in the southern hemisphere, 305 nanometer UV levels have gone up by some 6 percent on average since 1979.
The primary culprit: decreasing levels of stratospheric ozone, a colorless gas that acts as Earth’s natural sunscreen by shielding the surface from damaging UV radiation.
The finding reinforces previous observations that show UV levels are stabilizing after countries began signing an international treaty that limited the emissions of ozone-depleting gases in 1987. The study also shows that increased cloudiness in the southern hemisphere over the 30-year period has impacted UV.
Jay Herman, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., stitched together data from several earth observing satellites — including NASA’s Aura satellite, NOAA weather satellites, and commercial satellites — to draw his conclusions. The results were published in the Journal of Geophysical Research in February.
“Overall, we’re still not where we’d like to be with ozone, but we’re on the right track,” said Jay Herman. “We do still see an increase in UV on a 30-year timescale, but it’s moderate, it could have been worse, and it appears to have leveled off.”
In the tropics, the increase has been minimal, but in the mid-latitudes it has been more obvious. During the summer, for example, UV has increased by more than 20 percent in Patagonia and the southern portions of South America. It has risen by nearly 10 percent in Buenos Aires, a city that’s about the same distance from the equator as Little Rock, Ark. At Washington, D.C.’s latitude — about 35 degrees north — UV has increased by about 9 percent since 1979.
The southern hemisphere tends to have more UV exposure because of the ozone hole, a seasonal depletion of the ozone layer centered on the South Pole. There are also fewer particles of air pollution — which help block UV — due to the comparatively small numbers of people who live in the southern hemisphere.
Despite the overall increases, there are clear signs that ultraviolet radiation levels are on the verge of falling. Herman’s analysis, which is in agreement with a World Meteorological Report published in recent years, shows that decreases in ozone and corresponding increases in UV irradiance leveled off in the mid-nineties.
The Many Sides of Radiation
Shorter ultraviolet wavelengths of light contain more energy than the infrared or visible portions of sunlight that reach Earth’s surface. Because of this, UV photons can break atmospheric chemical bonds and cause complex health effects.
Longer wavelengths (from 320 to 400 nanometers) — called UV-A — cause sunburn and cataracts. Yet, UV-A can also improve health by spurring the production of Vitamin D, a substance that’s critical for calcium absorption in bones and that helps stave off a variety of chronic diseases.
UV-B, which has slightly shorter wavelengths (from 320 to 290 nanometers), damages DNA by tangling and distorting its ladder-like structure, causing a range of health problems such as skin cancer and diseases affecting the immune system.
As part of his study, Herman developed a mathematical technique to quantify the biological impacts of UV exposure. He examined and calculated how changing levels of ozone and ultraviolet irradiance affect life. For Greenbelt, Md., for example, he calculated that a 7 percent increase in UV yielded a 4.4 percent increase in the damage to skin, a 4.8 percent increase in damage to DNA, a 5 percent increase in Vitamin D production, and less than a percent of increase in plant growth.
“If you go to the beach these days, you’re at slightly higher risk of getting skin cancer (without protection),” Herman said, though he noted the risk would have been even greater in the absence of regulations on ozone-depleting substances.
Last year, one of Herman’s Goddard colleagues, Paul Newman, published a study showing that the ozone hole likely would have become a year-round fixture and UV radiation would increase 650 percent by 2065 in mid-latitude cities if not for the Montreal Protocol, an international treaty signed in 1987 that limited the amount of ozone-depleting gases countries could emit.
Clouds and Hemispheric Dimming
In addition to analyzing ozone and ultraviolet trends, Herman also used satellite data to study whether changes in cloudiness have affected UV trends. To his surprise, he found that increased cloudiness in the southern hemisphere produced a dimming effect that increased the shielding from UV compared to previous years.
In the higher latitudes especially, he detected a slight reduction — typically of 2 to 4 percent — in the amount of UV passing through the atmosphere and reaching the surface due to clouds. “It’s not a large amount, but it’s intriguing,” Herman said. “We aren’t sure what’s behind it yet.”
Vitali Fioletov, a Canadian scientist and member of the World Meteorological Organization’s advisory group on ultraviolet radiation, agreed that Herman’s findings about cloudiness warrant additional investigation. “I found the cloud effects on the global scale to be the most interesting aspect of the study,” he said. “This isn’t something you could see without satellites.”
Herman synthesized measurements from the Total Ozone Mapping Spectrometer (TOMS) aboard Nimbus 7 and Earth Probe, the Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite, NASA’s Sea-Viewing Wide Field-of-view sensor (SeaWiFS) on the commercial SeaStar satellite, and the Solar Backscatter Ultraviolet Instrument (SBUV) on several polar orbiting NOAA weather satellites.
Related Links:
Global increase in UV irradiance during the past 30 years (1979–2008) estimated from satellite data
h/t to Dr. Leif Svalgaard
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Since most of the freon was produced and released in the Northern Hemisphere, why has the Southern Hemisphere seen the greatest effect?
Clouds
They reduce Uv radiation. But the article begins with an emphasis on ozone. How about the thousands of lightning strikes ever 24 hours on this planet that create ozone. What about the dry copiers and printers in offices that create ozone.
How about the wind turbine blades that are made without UV inhibitors and will break down with ultraviolet degradation?
“It’s not a large amount, but it’s intriguing,” Herman said. “We aren’t sure what’s behind it yet.”
“I found the cloud effects on the global scale to be the most interesting aspect of the study,” he said. “This isn’t something you could see without satellites.”
The science is, of course, still settled.
Doesn’t this link to solar cycles being powerful until recently?
” at one line of latitude — 32.5 degrees — a line that runs through central Texas in the northern hemisphere and the country of Uruguay in the southern hemisphere..” (second paragraph)
You are mixing up latitude and longitude here, latitude lines do not run through both hemispheres. Please correct.
[Fixed, thanks. ~dbs, mod.]
I blame the “Clean Air Act”
Are we all going to die then?
One thing straight off the bat … what is the actual amount of the change, and not the percent? If one factors in latitude (lower effective solar angle at higher latitude), the percent changes may be larger at high latitudes, but what’s the real magnitude of the absolute changes? Moreover, the geographic area also plays a role … so that we end up with higher percentage changes in UV levels, but in areas with low solar angles and over much smaller areas of land. The graphical contours over the tropical latitudes (plus/minus 2.5%) … are those midpoints? Greater-than contours?
These are questions to ask, because I really distrust graphics like this as it is too easy to make it appear more dramatic than it is. Or perhaps this one is OK … I would just like to know.
“Last year, one of Herman’s Goddard colleagues, Paul Newman, published a study showing that the ozone hole likely would have become a year-round fixture and UV radiation would increase 650 percent by 2065 in mid-latitude cities if not for the Montreal Protocol, an international treaty signed in 1987 that limited the amount of ozone-depleting gases countries could emit.”
Let me go on record as being skeptical of that claim.
As for the observations… if the readings hold up (no drifting, coverage, etc), I think it’s a great addition to science.
As for the interpretations and projections… let the arguments begin!
WASHINGTON — It may sound far-fetched, but federal regulators are studying whether sudden acceleration in Toyotas is linked to “cosmic rays”.
Radiation from space long has affected airplanes and spacecraft, and is known for triggering errors in computer systems, but has received scant attention in the auto industry.
The questions show how deep regulators and automakers may have to dig to solve the mysteries of sudden acceleration. Toyota says it is fixing mechanical problems — floor mats and sticky pedals — that explain sudden acceleration in 13 models totaling 5.6 million vehicles.
Isn’t James Hansen the astrophysicist?
Are you telling me that high UV is not caused by AGW?
How dare you?
So we analyse satellite measurements of atmospheric conditions and gases to model what radiation would be measured at ground level?
Smells from herring.
The largest increases in UV (shown in white, red, orange, and yellow) have occurred in the southern hemisphere during summers.
During winters….
Leif Svalgaard (08:26:59) :
The largest increases in UV (shown in white, red, orange, and yellow) have occurred in the southern hemisphere during summers.
During winters….
It sure would be interesting to see the time scaled changes verse the end point averages. Then see how that maps to albeto and temp change.
“Since most of the freon was produced and released in the Northern Hemisphere, why has the Southern Hemisphere seen the greatest effect?”
Perhaps because the annual South Pole Ozone Hole is much larger than the annual North Pole Ozone Hole.
This is interesting!
What impact, if any, does this increase in UV radiation have on the warming we have experienced since 1978?
It would be interesting to know if some fraction of the warming since 1978 was due to this UV radiation increase – and therefore not due to CO2 or carbon black or land use change or methane or . . .
Also – does UV radiation have more of an impact on urban areas? Absorbed better by asphalt or concrete? Or is all radiation (visible light etc.) pretty much the same.
This may come as a shock to Jay Herman but June when the ozone peaks is winter in the southern hemisphere. Even in NZ (35°-50°S), very few people are on the beach at that time. Skfield maybe but not much flesh is exposed.
If NASA can’t get a basic fact like this right, what hope have we?
I’ve always heard about the change in exposure. Does anyone know what the exposure is in absolute terms? Was the southern hemisphere previously less exposed than the northern? Any proxies for long-term reconstruction?
This is very interesting. I agree with the need to better understand the effect of clouds. One aspect of the article puzzles me a bit however. All kinds of percentages were given but few absolute values, i.e. the data. Nor was any clear picture give of what those percentages were to mean. I strongly suspect that a small percentage increase in plant growth is far more important, has a much greater magnitude, then even a large percentage in skin cancer rate potential. Readers may wish to read my essay on data at: retreadresources.com/blog
I will upgrade my sun cream to factor 20 to 30 and wear a Panama hat wherever I go!
No serious, skin cancer is on the rise, what do I say, it’s exploding!
I have several friends who are in their forties who receive treatment for skin cancer, nose ears, neck and I tell you it’s not a walk in the park.
I spend a lot of time in the mountains and fairly disciplined in taking my precautions but I still get burned once in a while.
Some times it only takes a few minutes to get a nasty burn.
However my friends hardly ever go into the mountains.
They spend some time at the beach each year, non of them ever spend time under a solarium but what they all have in common is that they drive cabriolet’s during the summer time. No cap, no hat, just sunglasses and the wind in your hair!
The hours spend behind the wheel of a cabriolet can really add up and who thinks about sun protection when you’re driving a car?
Too many people are unaware of the dangers!
Henry chance, impossible! Who would the lawyers sue it it were true? Anyway I think Hansen wears a tinfoil hat most of the time so he’s not qualified.
O3 filters UV, but not all
O2 mostly lower in atmosphere than O3
UV strikes O2 breaking the molecules up and producing O3
O3 layer increases in size
filtering out more UV
resulting in less O3 production
At top of O3 layer different UV frequencies break O3 down to O2 plus O. Left over O finds another left over O to party with.
So… thickness of O3 layer depends on intensity variations of UV destroying O3 at top, and rate of production of Ozone at bottom production going up in a thin ozone layer, and going down in a thick one, maintaining it at a reasonably constant thickness.
But at the poles sun’s radiance is steeply inclined so destruction rates fall, but production rates fall further. Hence a depression or “hole” appears. The arctic depression is smaller than the antarctic depression because the arctic’s summer “recovery period” happens when earth orbit is closest to sun, hence stronger rays and the antarctis further, hence less recovery when incliniation to the sun favours additional production.
As I recall, the CFC catalyst reaction that kicks of the ozone destruction thing needs a temperature range higher than what the ozone layer is at.
At poles
2nd line above should read
O2 mostly lower in atmosphere than O3
[Noticed & fixed even before this comment. ~dbs, mod.]
OT – both Michael Mann and Judith Curry were interviewed by Discovery Magazine. Quick read has Mann callling Curry an almost skeptic. Only Discovery magazine would consider this a “balanced” article.
Jay
(engineering is more fun!)
There is no ozone hole.
There is no zone in the ozone layer devoid of ozone. The layer is thinner in the poles, but it is not without any trace of ozone, which is what street people understand as “a hole”
Ozone is created in the stratosphere when highly energetic solar rays strike molecules of oxygen (O2) and cause the two oxygen atoms to split apart. If a freed atom bumps into another O2, it joins up, forming ozone (O3). The poles receive less quantity of highly energetic solar rays, that is one of the reasons why the ozone layer is thinner in the poles, and unless somebody demonstrates otherwise, it has been always that way.