Earthshine reflected off the moon shows no trend during the Pause

About a third of the sunlight that hits Earth gets reflected back out to space mainly by clouds, ice or bare earth. A small change in this can make a big difference to the global energy balance. And the energy balance is kinda “everything” in the climate debate. So this new paper by Palle et al really ought to attract quite a bit of interest. But for lots of reasons real data was never going to provide much joy for most climate scientists.

The thing is, climate models predict that CO2 will cause warming, which will in turn cause ice to melt and the albedo to get smaller, which will cause more warming… it’s a positive feedback. So if albedo was shrinking during the last 2 decades, the Crisis Team could say the models were right about albedo, but then, golly, they were even more wrong about that warming that didn’t happen. On the other hand, if albedo was growing, they could add it to the list of excuses for The Pause and write headlines like: Global clouds increase — hiding the effect of CO2! But then skeptics could point out that if more CO2 causes more reflective clouds, the albedo may act as negative feedback — disaster averted.

But back to that data. One of the ways to measure albedo, can you believe, is to track Earthshine — the light that the Earth shines on the dark side of the moon. Obviously Earthshine is the lucky lotto-winning-light that reflects off Earth and hits the Moon, and then reflects back again to Earth again.

A new study by Palle puts together 16 years of data on this and finds there are big changes from year to year but overall there is no trend, which rather fits with The Pause.

Somehow, strangely, even though Life on Earth depends on calculating our Energy Balance, the golden river of climate gravy is not running through the land of Earthshine research. The researchers shifted from a meagre one telescope up to two in 2006. There’s a big gap in the global data in Figure 2 when that happened (see below). But even two telescopes are barely adequate. Palle et al estimate that with eight automatic robotic stations they could achieve 2 – 3 times the precision they have now. But while we can find funds to subsidize 225,000 wind towers, we can’t afford to do the proper basic research that might tell us whether we needed those 225,000 wind towers. Crony-renewables anyone?

If there is a crisis in our global energy balance, a lot of people don’t seem to be taking it seriously.

Abstract The Earth’s albedo is a fundamental climate parameter for understanding the radiation budget of the atmosphere. It has been traditionally measured from space platforms, but also from the ground for sixteen years from Big Bear Solar Observatory by observing the Moon. The photometric ratio of the dark (earthshine) to the bright (moonshine) sides of the Moon is used to determine nightly anomalies in the terrestrial albedo, with the aim is of quantifying sustained monthly, annual and/or decadal changes. We find two modest decadal scale cycles in the albedo, but with no significant net change over the sixteen years of accumulated data. Within the evolution of the two cycles, we find periods of sustained annual increases, followed by comparable sustained decreases in albedo. The evolution of the earthshine albedo is in remarkable agreement with that from the CERES instruments, although each method measures different slices of the Earth’s Bond albedo.

REFERENCES

Palle, E., et al. (2016), Earth’s albedo variations 1998-2014 as measured from ground-based earthshine observations, Geophys. Res. Lett., 43, doi:10.1002/2016GL068025.

Taking shots of the Moon? Bob King, of Sky and Telescope explains the finer details: To take your own photo like this, you need to get up just before dawn on April 6th (probably not possible now) to see the last tiny sliver of the moon. April 7th is a new moon. April 8th we’ll see a sliver of the waxing moon just after the sun sets. The post there counts the hours after the new moon occurs… Moongiant tracks the phases.

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