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How the media is getting the Arctic seabird droppings/cloud formation/warming story wrong

George Divoky, November 30, 2016

Originally posted to the PSG Listserve on 18 November:

Because of the coverage of the U.S. presidential election in the past year, we don't need to be reminded that the media fails us in many ways - including making the trivial seem important and poorly covering those things that are important.

A recent interesting paper in Nature Communications:

Contribution of Arctic seabird-colony ammonia to atmospheric particles and cloud-albedo radiative effect

reports that "model simulations indicate that the pan-Arctic seabird-influenced particles can grow by sulfuric acid and organic vapour condensation to diameters sufficiently large to promote pan-Arctic cloud-droplet formation in the clean (sic) Arctic summertime."

Many "news" sources, including a number that should really know better, have taken to the story and of course have presented it in a way that will do more to attract than inform their readers:

"Seabird poop is helping to keep the Arctic cool, researchers say" - Cantech Letter, "How Bird Poop Helps Cool the Arctic" - Science magazine, "How Bird Poop Could Help Keep the Arctic Cool" -, "Climate Change: Will Bird Poop Save The World As Arctic Winters Get Warmer?" - International Business Times, "Seabird Crap Could Help Save the Arctic"

The piece on the Popular Science website

ends by saying ""Our study just highlights one connection," Croft says. But it's a good reminder that the migration patterns of animals – which are shifting in the wake of climate change—might help keep our planet running as usual."

The source of the last sentence is not clear but it gives the general reader the impression that those studying climate and/or migratory animals need to be regularly reminded that "migration patterns of animals.....might keep our planet running as usual" and that the results of this study provide that reminder.

Ignored in all this are the findings that clouds have been shown to not affect the rate of Arctic warming:

"There's no cloud response in summer to melting sea ice, which means it is likely that clouds are not slowing down the Arctic climate change that is happening—clouds aren't really providing the expected stabilizing feedback"

and that they can actually increase the rate of melting

Meanwhile the current warming in the Arctic is unprecedented and also "insane" as the Washington Post reports

Comments ( 2 )

David Schutt

Very timely. Thanks for posting.

George Divoky

Some comments from a physical scientist with who I shared my original post and who knows much more about CCNs (cloud condensation nuclei) than I do.

It is true that the summertime Arctic is generally 'pristine' if you mean relatively free of industrial pollutants. In situ and aerosol optical depth measurements from a network of stations show the summertime min in concentration and atmospheric turbidity. Despite, the Arctic is cloudiest during the summer months, sometimes exceeding 90% and Arctic stratus dominate, so there is no shortage of natural CCN to produce cloud droplets. Sea salt aerosols, DMS, and probably this mechanism involving ammonia are natural sources. Incursions of fire smoke and other pollutants are episodic and therefore have small effect, not all make good CCN.

A few things that do not come out in the article;

The Arctic is already mostly cloud covered during summer and natural sources of CCN have always been there, including the bird contribution, so any CHANGE would require a significant change in bird population in this case. It is not clear if populations will increase or decrease, where and when etc. effect of this process is probably much smaller than simulated, near negligible although I cannot prove that. If I am correct, you double population and the source and you still have negligible impact.

the sources are only around the perimeter of the basin and concentrated at colonies. "Bursts" may occur and produce local effect according to the process they document, but I seriously doubt the dispersion of these particles have more than very localized impact on cloud albedo on scale they claim via indirect effect. That is, I question the model output and the estimate of radiative forcing they claim. Again, this is not a new phenomenon, so it is the change that will be important when evaluating climate impacts.

The other studies you refer to are legitimate in that they use real data and arrive at results empirically to show the sea ice loss in summer has not impacted cloud distributions measurably. Cloud anomalies most likely contribute to sea ice variations during summer and these in turn are driven by atmospheric dynamics, not necessarily a response to the ice distribution; advection plays a major role.

The longwave impacts of changing cloud microphysics are ignored as you point out. During summer the thermal emissions and albedo effects of clouds compete and effects are variable, depending on surface albedo; net effect in question. It is true, however, that the LW dominates beginning in autumn and the indication is that the delay in sea ice has increased cloud cover and thus enhanced warming, a positive feedback far far greater in effect than any additional cooling that might result from increasing bird populations.

Here is another study that shows the effect:

Influence of Arctic sea ice extent on polar cloud fraction and vertical structure and implications for regional climate – Palm et al. (2010) “Recent satellite lidar measurements of cloud properties spanning a period of 5 years are used to examine a possible connection between Arctic sea ice amount and polar cloud fraction and vertical distribution. We find an anticorrelation between sea ice extent and cloud fraction with maximum cloudiness occurring over areas with little or no sea ice. We also find that over ice-free regions, there is greater low cloud frequency and average optical depth. Most of the optical depth increase is due to the presence of geometrically thicker clouds over water. In addition, our analysis indicates that over the last 5 years, October and March average polar cloud fraction has increased by about 7% and 10%, respectively, as year average sea ice extent has decreased by 5%–7%. The observed cloud changes are likely due to a number of effects including, but not limited to, the observed decrease in sea ice extent and thickness. Increasing cloud amount and changes in vertical distribution and optical properties have the potential to affect the radiative balance of the Arctic region by decreasing both the upwelling terrestrial longwave radiation and the downward shortwave solar radiation. Because longwave radiation dominates in the long polar winter, the overall effect of increasing low cloud cover is likely a warming of the Arctic and thus a positive climate feedback, possibly accelerating the melting of Arctic sea ice.