Clouds and Global Temperature

[blizzard1024]

It is really hard to find global cloud cover percentages but I finally found this graph which comes from

The International Satellite Cloud Climatology Project (ISCCP). It shows decreasing cloud cover

until the late 1990s where is appears to stabilize. This could explain why we have plateaued 

in the global temperatures since the late 1990s. The cloud cover decreases from the early 1980s

to the late 1990s of which temperatures rose, then cloud cover stabilizes at a lower level and so does

global temperature. 

 

See cloud cover graph from ISCCP and HadCRUT V3/4 temperature graph. Is this cloud cover data accurate?

I have never heard of ISCCP before but this dataset's cloud cover data looks to modulate global temperatures

as one would expect. 

 

 

 

[FloridaJohn]

Interesting. If you are interested in cloud cover, you may want to check out this recent article over at realclimate.org From that article:

 

The complexity of the cloud feedback means that it is difficult to observe and evaluate. Ideally, we would have accurate global observations of clouds for a number of decades to compare to the climate models. However, without that, we have to estimate cloud feedbacks using the shorter high-quality observational record, and then try to relate the short-term behavior to long-term (century-scale) cloud feedbacks. For some feedbacks, such as the water vapor and ice-albedo feedbacks, there has been some success in evaluating models directly using observations. For example, the modeled water vapor feedback in response to the eruption of Pinatubo agrees with the satellite data (Soden et al., 2002), while modeled Northern Hemisphere (NH) snow and sea-ice feedbacks underestimate the observed feedback (Flanner et al., 2008). Evaluation of cloud feedbacks has been less successful, due to the difficulty of obtaining homogenous global cloud properties from either satellite or surface-based observations. Many assumptions (such as for cloud droplet size or vertical distribution) must be made for these retrievals, and instrument and calibration errors may still be significant. Additionally, there isn’t an obvious correspondence of the short-term cloud behavior with the long-term behavior in climate models (Dessler, 2010; Masters, 2012).

 

Also, one little nit to pick, your charts would be easier to interpret if you used the same timescale on both of them.

[blizzard1024]

Interesting. If you are interested in cloud cover, you may want to check out this recent article over at realclimate.org From that article:

 

The complexity of the cloud feedback means that it is difficult to observe and evaluate. Ideally, we would have accurate global observations of clouds for a number of decades to compare to the climate models. However, without that, we have to estimate cloud feedbacks using the shorter high-quality observational record, and then try to relate the short-term behavior to long-term (century-scale) cloud feedbacks. For some feedbacks, such as the water vapor and ice-albedo feedbacks, there has been some success in evaluating models directly using observations. For example, the modeled water vapor feedback in response to the eruption of Pinatubo agrees with the satellite data (Soden et al., 2002), while modeled Northern Hemisphere (NH) snow and sea-ice feedbacks underestimate the observed feedback (Flanner et al., 2008). Evaluation of cloud feedbacks has been less successful, due to the difficulty of obtaining homogenous global cloud properties from either satellite or surface-based observations. Many assumptions (such as for cloud droplet size or vertical distribution) must be made for these retrievals, and instrument and calibration errors may still be significant. Additionally, there isn’t an obvious correspondence of the short-term cloud behavior with the long-term behavior in climate models (Dessler, 2010; Masters, 2012).

 

Also, one little nit to pick, your charts would be easier to interpret if you used the same timescale on both of them.

 

Thanks. I will take a look. I will resize these graphs when I have a chance and repost.

[blizzard1024]

Thanks. I will take a look. I will resize these graphs when I have a chance and repost.

Here are the graphs again. The cloud fraction goes from 1983-2009 with

the global temperatures from 1979-2012 in this case. 

[Ellinwood]

I have no stake in this, but I just wanted to provide an image that was easier to see the similarities/differences between the graphs.

I approximately matched up the time scales, inverted the cloud cover % and placed it just below the other graph so you can see the trends without overlapping the variables.

[blizzard1024]

I have no stake in this, but I just wanted to provide an image that was easier to see the similarities/differences between the graphs.

I approximately matched up the time scales, inverted the cloud cover % and placed it just below the other graph so you can see the trends without overlapping the variables.

cloudcover_temps.png

nice. thanks. 

[skierinvermont]

I have corresponded directly with the director of ISCCP and he has explained that it is not intended to be accurate long-term. The trend of the graph is not correct. It's intended to be used for short-term data. So you can look at 1995-1998 and see that cloud cover went up or down. Long-term there are too many issues with piecing together data from different satellites and calibrating them. 

[blizzard1024]

I have corresponded directly with the director of ISCCP and he has explained that it is not intended to be accurate long-term. The trend of the graph is not correct. It's intended to be used for short-term data. So you can look at 1995-1998 and see that cloud cover went up or down. Long-term there are too many issues with piecing together data from different satellites and calibrating them. 

That's too bad we don't have accurate long term cloud fraction data.  

[skierinvermont]

That's too bad we don't have accurate long term cloud fraction data.  

 

Yeah it is considering it's one of the largest uncertainties aside from aerosols. There are a few other sources of data out there though that give some idea of what might be happening, but they have large uncertainty (error bars).