Spread the love

Guest Post by Willis Eschenbach

Albedo is the percentage of incident light that is reflected by an object. For years, I’ve read claims that the loss of Arctic sea ice is a positive feedback. It is logical—warming leads to less ice, less ice reduces the surface albedo; reduced surface albedo means more sunlight is absorbed; more sunlight absorbed leads to increased warming. Positive feedback. What’s not to like?

For example, in 2019 the IPCC said:

Feedbacks from the loss of summer sea ice and spring snow cover on land have contributed to amplified warming in the Arctic (high confidence).

Wim Rost pointed me to an interesting 2007 NASA article about Arctic albedo which says:

Although sea ice and snow cover had noticeably declined in the Arctic from 2000 to 2004, there had been no detectable change in the albedo measured at the top of the atmosphere: the proportion of light the Arctic reflected hadn’t changed. In other words, the ice albedo feedback that most climate models predict will ultimately amplify global warming apparently hadn’t yet kicked in.

Kato quickly understood why: not only is the Arctic’s average cloud fraction on summer days large enough—on average 0.8, or 80 percent—to mask sea ice changes, but an increase in cloudiness between 2000 and 2004 further hid any impact that sea ice and snow losses might have had on the Arctic’s ability to reflect incoming light. According to the MODIS observations, cloud fraction had increased at a rate of 0.65 percent per year between 2000 and 2004. If the trend continues, it will amount to a relative increase of about 6.5 percent per decade. At least during this short time period, says Kato, increased cloudiness in the Arctic appears to have offset the expected decline in albedo from melting sea ice and snow.

Wim suggested that I take a look to see if this process, of the changes in cloud albedo counteracting the changes in surface albedo, had continued up to the present.

Fortunately, the CERES data allows us to calculate the trends in both the surface albedo and the top-of-atmosphere (TOA) albedo. First, here’s the trend in surface albedo in percent per year, on a 1° latitude by 1° longitude basis.

Figure 1. Atlantic and Pacific centered views of the trend in surface albedo, in percent per year. Seasonal variations removed.

As expected, due to the reduction in Arctic sea ice, the albedo in the Arctic has indeed decreased significantly over the 21-year period. It’s decreased at a rate of 0.28% per year, a total of almost 6% over the 21 year period. Note also that the poles are the only part of the surface with a significant trend.

Next, here’s the top-of-atmosphere (TOA) albedo trend.

Figure 2. Atlantic and Pacific centered views of the trend in TOA albedo, in percent per year. Seasonal variations removed.

Amazing. The increase in cloud albedo has almost totally counteracted the decrease in Arctic surface albedo. The change is only six-hundredths of a percent per year, basically lost in the noise. The effect of the clouds has brought the polar regions back into line with the rest of the planet.

This inspired me to look at the correlation of the surface albedo and the cloud albedo over the period. Positive correlation of two variables means generally that when one increases, so does the other. Negative correlation means that they move in opposite directions. Figure 3 shows that result.

Figure 3. Correlation, surface albedo and cloud albedo.

This is also most interesting. It shows that the cloud albedo not only counteracts the sea ice albedo changes. It also counteracts the changes in surface albedo from snow and land ice. Not only that, but in the area of the sea ice, the correlation is around -1, meaning that surface albedo and cloud albedo move in nearly total opposition..

Examining Figure 3, it is obvious that over the land the correlation is negative almost everywhere. However, over the ocean, the correlation is clearly related to the temperature. As the Figure 4 scatterplot below shows, wherever the ocean is below about 22°C, the clouds tend to oppose any change in surface albedo.


Figure 4. Scatterplot showing the correlation of cloud and surface albedo trends versus surface temperature. Data is the gridcell-by-gridcell 21-year average values. Yellow/black line is a LOWESS smooth of the data.

Again, in the sea ice area where 21-year average temperatures are around zero, the negative correlation is almost perfect.


With those results in mind, let me return to the 2019 IPCC claim:

Feedbacks from the loss of summer sea ice and spring snow cover on land have contributed to amplified warming in the Arctic (high confidence).

Note that despite the IPCC claim of “high confidence”, the 2007 findings of Kato and the more recent CERES data shown above demonstrate that feedback from changes in sea ice and snow cover have NOT contributed in any significant way to amplified warming in the Arctic. Cloud changes offset these sea ice and snow changes almost entirely. In short, the IPCC claim is overstated.

This highlights the problem with the claim that we should all listen to the “97% consensus” … it’s meaningless. Science is the process of overthrowing the consensus.

My best to all on a lovely fall day,


PS—As usual, I ask that you quote the exact words that you are discussing. For the reasons why, see here.

via Watts Up With That?


October 3, 2021