To climate Experts--What is the effect of Albedo change due to snow shoveling

The answer is "not a lot". Clearing the Arctic Ocean of sea ice is the sort of thing you need to get a perceptible effect.

-- Bill Sloman, Nijmegen

Since the earth is 70% water, were really screwed!

Cheers

I can't do the calculation. I'll suggest you look at larger issues:

The heat island effect has been done to death, already. Although the debate will continue for a time, it's considered for now to be minor and accounted for. There are papers on the subject. David Parker's "Climate Large-scale warming is not urban" comes from 2004 and concludes, "Urban heat islands occur mainly at night and are reduced in windy conditions. Here we show that, globally, temperatures over land have risen as much on windy nights as on calm nights, indicating that the observed overall warming is not a consequence of urban development." In 2003, a little earlier, Peterson's, "Assessment of urban versus rural in situ surface temperatures in the contiguous United States: No difference found" concluded, "Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures."

On the other hand, Kalnay and Cai claimed that urbanization and land-use change had an effect on the US climate. They used surface temperatures obtained from NCEP/NCAR 50-year reanalyses (NNR) and their difference compared with observed station surface temperatures as the basis for their conclusions, on the grounds that the NNR did not include these anthropogenic effects. However, the NNR also overlooked other factors such as known changes in clouds and surface moisture, which are considered more likely to explain the findings.

Wiki has an okay article on the topic:

I believe it's now generally considered "bounded-small" by various other well-chosen observations that attempt to extract the effect's magnitude. More time is probably needed to be certain, but the effect doesn't seem significant. In space, I think it's ERBE and CERES that help examine changes in Earth's albedo from that perspective, but so far the data doesn't appear support concluding significant changes from shoveling driveways. In fact, I think the suggestion is that in the case of the heat island effect, it is more about the reduced cooling that occurs at night when the surface that might otherwise radiate to space is instead blocked by buildings -- not driveways shorn of their snow during the day.

Reasonable question to ask. But it is being looked at.

Jon

Albedo >0.9

Only in contrast to the snow. Your eyes decieve you. Very few natural surfaces are truly black. The darkest tarmac roads still reflect about

10% of the light that hits them and a wet surface reflects another 4-5%.

Effective Albedo ~ 0.15

See for example

Most tarmac is roughly like basalt in colour some are lighter and some are darker depending on the crushed rock used and wear factors.

Using rough numbers it is possible with the simplifying assumption that the entire of the US is snow covered to put an upper bound on it. I will leave it as an excercise to the reader to recompute this for the snow covered states. Taking the roads by category BTS 2006 table gives

Interstates 47k miles x 100m = 8G m^2 Principle 400k miles x 50m = 32G m^2 Minor 800k miles x 25m = 32G m^2 Local 3M miles x 10m = 48G m^2

Total area of US roads = 120G m^2 = 120,000 km^2

We can haggle about the road dimensions, but I think I have been fairly generous on lane widths here.

Sounds a lot doesn't it. But compared to the total area of the USA of

9,000,000 km^2 it represents a whopping 1.3% at most as an upper bound.

In practice most roads in the sub tropical states are seldom covered in snow. It is only meant as a rough guide. So instead of an albedo of 0.90 if the entire of the USA were perfect powder snow covered clearing all the roads would bring the national albedo down to 0.89 which is not a lot.

If you wanted to know the effect globally of Americans shovelling snow you would have to multiply by (area of US/area of the world) ~ 9/500 So the Earth's albedo is affected in the fourth or fifth decimal place in the worst case.

Plenty of other effects are much stronger most notably dust and ash from smoke settling on the fresh snow and locallised melting. Only the freshest cleanest dry powder snow has albedo 0.90 it quickly degrades.

Regards, Martin Brown

Even that is not so clear cut. The insolation in the arctic is not particularly far from the horizontal, and a lot will reflect off the surface of the sea.

Sylvia.

Which just goes to show that mankind is powerless against nature.

Cheers

Ian

The "global warming problem" was solved in the late 1960's - just paint Texas white. ;-)

Cheers! Rich

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i'm not sure the albedo of a forest or other rough surface gets really high even when it's snowy.

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ok, someone answered with a real number! thank you

But lets consider all the snow shoveling in the world not just the US, so maybe the warming effect of all the snow shoveling and snow clearing off of structures etc is in the 3rd decimal place...

Here is the key to my point.

How does that level of heating due to anthropomorphic snow clearing compare to the alleged heating effect due to measured increase in CO2?

Mark