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With the increase in carbon dioxide and the warming of the Earth's surface, some surfaces change colour and reflect light differently. In general, there is a decrease in light areas and an increase in dark areas.

Can the measurement of the albedo show this difference, or is it too small?

Jean Dumont
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  • I think the effect of CO2 is way too complicated than in the picture you have in mind. Rather than increasing a T that is even difficult to be defined, it does surely increase the amount of energy kept by Earth. Nothing changes as compared to a mapping as it is. Note that at least in principle the effect of CO2 should be be seen in the infrared. I am not a specialist I just apply basic concepts, here. Moreover parts of your question seems to involve detection of CO2 induced changes on surface features. Obviously if a region gets arid its albedo changes as well. Perhaps you could clarify the Q – Alchimista Feb 05 '20 at 13:22
  • "In general, there is a decrease in light areas and an increase in dark areas." [citation needed] not saying it isn't true, just that it seems like a big thing to assert. – Semidiurnal Simon Feb 11 '20 at 10:29
  • Answerers: Please don't forget the last part of the question! If we have somebody who knows, would be interesting to know how earth's albedo is measured (is it measured? or calculated?) – Semidiurnal Simon Feb 11 '20 at 10:31

2 Answers2

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The two biggest changes are fairly straight forward. Ice cover and Ocean area. During the peak of the last ice age, ice extended over most of Canada, maybe half of Russia and parts of the Northern United States and snow probably extended well south of that during winter. Ice has a high albedo.

As glaciers grow, ocean cover decreases. The yellow on this map indicates loss of ocean cover and increase in land. Oceans have low albedo, which means shrinking oceans also raises Earth's albedo. As a rule, during glaciation periods, Earth's albedo is higher and more light gets reflected directly back into space, which fits with the planet getting colder. This is one of the ice age feedback mechanisms.

enter image description here

Source of image.

Other factors may be less predictable, like deserts have comparatively high albedo and forests, lower albedo and the Sahara, for example, becomes partially forested over depending on variations in weather patterns driven primarily by Milankovich cycles (not necessarily in sync with ice age cycles), but I suspect, compared to the ice and ocean surface area changes, desert to forest changes have less effect.

Today's global warming is expected to (and already has) decreased ice and show cover, which lowers albedo and this trend is expected to continue. Over time, enough glacial ice might melt that oceans become measurably larger as well. This ice melt and ocean expansion lowers albedo further and is one of the positive feedbacks that effects and is expected to continue to effect man made climate change.

userLTK
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    don't forget changes in clouds. – Semidiurnal Simon Feb 11 '20 at 10:29
  • @SemidiurnalSimon Yes, clouds too. I guess I wanted to avoid that can of worms. Clouds get pretty complicated. I'm not sure there's a direct correlation between CO2 and cloud formation, it depends in part on weather patterns. It's also harder to know how many clouds there were, for example, during the last glaciation. Some studies say the PETM basically lost it's high altitude clouds, adding to warming but it's a complicated subject. I'm not sure I could do the cloud modeling part of this answer justice. – userLTK Feb 11 '20 at 19:24
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    I interpreted "terrestrial albedo" as meaning the surface albedo rather than the TOA planetary albedo, in which case clouds aren't an issue. Might need clarification from the OP. – Deditos Feb 11 '20 at 21:36
  • @userltk fair enough! – Semidiurnal Simon Feb 12 '20 at 06:35
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In addition to the other answer (which I think covers the really big effects), things like changes in vegetation type and amount, which can happen as a result of change in temperature (as well as because, for instance, humans both cultivate crops and remove or even plant forests) change the albedo. However this change is complicated: vegetation typically lowers albedo, but it also increases evaporation of water (known as 'evapotranspiration' which tends to cool the surface.

These changes are certainly modelled in some earth system models (see for instance UKESM), and things like vegetation cover and type is the sort of thing that can be observed by satellites: see this NASA page for instance. Additionally albedo can be measured directly: see for instance this page (also NASA). So these changes certainly do change albedo measurably, although I suspect to a smaller extent than large-scale changes in ice cover.