Last week I showed projections of changes in the UV for the month of April from a pre-print in a recently-published paper. It turns out that there were some even better plots in their final published version. In case you didn’t have time to follow that link to it, I’ll show a couple of them here, including the much more interesting month of October, where the patterns of change are dominated by dramatic decreases in Antarctic ozone during the ozone ‘hole’ period. I’ll also include a couple of their figures that illustrate the relative importance of ozone changes compared with the other factors involved (i.e., changes in aerosols, clouds, and surface reflection).
The multi-panel figure below shows global maps of the percentage changes in local-noon UVI under all-sky conditions for the months of January, April, July, October and for the annual mean. The first row shows changes from the 1950s to the 1990s. The next three rows show the projected changes from the 1950s the 2090s for three different climate-change emission scenarios
Low carbon emissions (SSP1-2.6)
Intermediate emissions (SSP3-7.0), and
High emissions (SSP5–8.5).
In all plots, areas of increasing UV are shown in red (and yellow for biggest increases), while areas of decreasing UV are shown in blue (and purple for the biggest decreases). The white shows areas with little or no change. The grey shading at latitudes higher than the green lines shows excluded areas where the UVI is too small to calculate realistic changes (i.e., for UVI < 0 .1).
Maps of the percentage changes in local-noon UVI (excluding areas with UVI < 0.1).
As I noted last week, future UVI changes vary regionally and depend critically on the climate change scenario. In the first future scenario (labelled SSP1-2.6) - the most optimistic for averting climate change - the UVI is projected to increase in most places. But for the other two it’s projected to decrease in most places, in some high-latitudes by more than 20 percent. The patterns of change are much more similar from month to month, though are notably more severe in October.
The two groups of multi-panel figures below show corresponding relative contributions to those changes in UVI that can be attributed to changes in ozone, aerosols, surface reflectivity, and clouds respectively. Patterns for January, April and July are similar, so here I’ve included just the plots for July in addition to the outlier ozone-hole month of October. Check out the paper if you’re particularly interested in what might to happen to UV at your place over those other months.
Percentage differences in the UVI due to changes in ozone, aerosols, albedo and cloud. Regions in grey are again excluded (UVI < 0.1).
The largest systematic changes are due to changes in ozone. In the earlier period, reductions in ozone contributed to widespread increases in UV, especially in October. But in the longer period, a projected recover,y in ozone will lead to increases in UV. For the latter two scenarios especially an expected overshoot in ozone will lead to widespread reductions in UV below 1950 levels by the end of the century.
Effects of changes in aerosols are also important regionally, especially over heavily populated areas where attempts to clean the air can contribute to increases in the UV. However, over most of the globe, increases in aerosols will contribute to increases in UV.
Over the earlier period (to 1990s), any changes in UV due to changes in surface reflectivity or clouds were small. But, due to increasing effects of climate change, changes could be larger for the latter period (to the 2090s). Over that period, reductions in surface reflectivity are expected to contribute to reductions in UV due to reduced ice cover, especially over the oceans at higher latitudes.
Projected patterns of change in UV due to changing cloud cover are the most difficult to characterize. In some places (especially at low latitudes) reductions in cloud cover will lead to increases in UV, whereas in others (especially at high latitudes), decreases in cloud will lead to increases in UV, especially over high latitude areas in summer.
In some regions, changes in clouds and surface reflectivity will contribute to changes in UVI greater than ±10 percent.
I think you’ll agree that the paper’s a nice piece of work. It must be if it got a double billing from me!
Like I said, it looks like a good news story. Of course, it remains to be seen if the predictions are correct. Only time will tell. Sadly, I don’t think I’ll be about by then.
On the plus side: that’s one of the nicest things about being a Climate Scientist rather than a Weather Forecaster. Everybody remembers when yesterday’s weather forecast was wrong, but nobody lives long enough to remember when the climate scientist gets it wrong.
P.S., with a CAUTION! If you’re a MAGA man(iac?), please read no further.
After the most recent tRumpian*** climate sabotage - delivered as promised (again), on day 1 of his tenure of terror - it looks less and less likely that there’s any chance of scenario SSP1-2.6 or anything like that optimistic path being followed. Every day’s delay is another nail in that coffin.
The orange bully wants to lock us into burning every last morsel of fossil fuels. He’ll be blissfully unaware that they will in any case have run out by the end of the century. But not until after the damage has been done. Hopefully though, he won’t get the notoriety he so desperately seeks (as the architect of the destruction of life as we know it). As Gwynne Dyer so eloquently reported, it already makes economic sense as well as environmental sense for the world to rapidly dump fossil fuels and adopt green energy solutions. And they’ll tap into unlimited supplies that can last for billions of years.
*** In years to come this term will surely be defined in the Concise Oxford Dictionary. Here’s my suggestion for the entry:
Ah. That feels SO MUCH better. I might get push-back from some. But only if they weren’t smart enough to heed that warning above.
I’d would welcome a tirade of tweets from twits like his tRumpiness. Others may have better suggestions for the proposed dictionary synonyms. Please use the ‘comments’ tool.
Belligerent, obstreperous come to mind?
Thanks again for highlighting another fascinating paper on UV