Albedo / Reflectivity

     Earth’s albedo fell from 29.36% at the end of 2000, to 28.72% at the start of 2025.  That’s 0.64%.

     Incoming sunshine, at the top of Earth’s atmosphere, averages 341.6 Watts / m2. (1366.4 Watts / m2 at Earth's disk spread across its spherical area is 1/4 as much.)

     Earth’s albedo change was 0.64% of 341.6 = 2.19 W / m2.

That's a lot.  Over 2000 to 2025, climate forcing (what induces planetary warming) was due 69% to Earth's darkening (see figure 2nd above) and only 31% (see 1st above) to added GHGs over the same period.  It used to be 50/50, and before that, GHG forcing predominated.  The warming effect of the albedo feedbacks are growing, relative to its GHG trigger, and already outweigh them.

Rapid Surge in Global Warming Is Mainly due to Earth's Lowered Reflectivity 0525.rtf

     The figure below, from Tselioudis (2024), shows that loss of cloud cover has been greater (more blue, back and gray) in the tropical North and South Atlantic Oceans than in the tropical North and South Pacific.

     The area low (%) in cloud cover in the tropical North Pacific grew from 11% to 21% from 1984 to 2018, which is 10° of latitude.  In the tropical South Pacific, the area low in cloud cover grew from 1° north to 21°south in 1984 (22° of latitude) to 6°N to 29°S over the same span, area low in cloud cover namely by 35° of latitude.  That's 13° of growth.  That 13° was a greater gain in the tropical South Pacific than the 10° for tropical North Pacific.

    In the tropical North Atlantic, over the same time period, the area low in cloud cover grew from 19° of latitude to 41°, (again, 22° of latitude change) over 34 years,  In the tropical South Atlantic, the area low in cloud cover increased by 21 to 34° of latitude, which is also 13° of latitude over 34 years.

     The narrow equatorial zone, with thicker (and thue more reflective) clouds shrank from 12% to 5% over the 34 years, or by 7%.

     In the mid-latitudes in the north Pacific, the area of dense (brown and red) cloud cover shrank from 20% to 17%, or by 3%.  In the Pacific's southern mid-latitudes, the area of dense cloud cover stayed at 26%.

     In the mid-latitudes in the North Atlantic, the area of dense (brown and red) cloud cover shrank from 25% to 18%, for 7% shrinkage.  In the South Atlantic md-latitudes, dense cloud cover shrank by perhaps only 1% over the 35 years. 

     The color-coded graph above, of % cloud cover over the Atlantic and Pacific Oceans (and their longitudinal portions of the Northern and Southern Oceans), translates to the graphs belows.

     Below at left, the latitude-weighted ocean cloud cover shrank from about 60% over 1984-87 to just over 53% in 2018.  That's 6 to 7%, or 0.2% per year.

     Below at right, the Atlantic Ocean is considerably less cloud-covered than the Pacific.  But both oceans' cloud covers shrank at similar rates, a little more over the Atlantic.  Latitude-weighted cloud cover shrank from a bit over 61% to 55% over the Pacific and from 57-58% to 50% over the Atlantic, across the 34 years.  % shrinkage was a little bit more over the Atlantic.

     Cloud cover shrinkage varies greatly by latitude, as shown below.  It is strongest in the low latitudes, 0-30°, and almost as strong at 30-40° latitude.  It weakens at 40-50° latitude and vanishes (or even reverses slightly) at 50-90° latitudes.

     The graphs below show the % cloud cover, disaggregated by ocean basin by latitude, over the same 34 years.  Observe that the hot regions at 10-40° north have no corresponding hot regions at 10-40° south.  That heat contrast on the map above shows in the southern Atlantic and Pacific graphs below, where the hotter equatorial regions have less % cloud cover than the cooler 10-30° south regions.

     Conclusion: % cloud cover is substantially less when and where oceans are hotter.  It seems very likely that warmer SSTs cause less % cloud cover.  Further investigation is warranted.

     Below left, the observations are the 3rd (right-most) of the 3 yellow to red graphs below.  The High ECS model (left-most of the 3) much more clearly matches OBSERVATIONs than does the middle (Low ECS) graph.  This is clearest in southern winter toward 60°S and in northern winter toward 60°N.  In addition, the 10-30°S patch from May to December in the High ECS model is a better match to observation than is the Low ECS (middle of 3) map/graph.

Why Clouds Are the Key to New Troubling Projections on Warming 0220.rtf - Newer global climate models (GCMs) do a much better job of handling clouds, for which droplet size is very important, as is large scale (10s to 100s of kilometers): micro and macro in the same model.
    These newer GCMs find that clouds diminish as Earth's surface warms.  See reasons in the figures below: How Climate Change Breaks Up Clouds.
    Thus, they have an amplifying effect on warming.  Note cloud figures with trend lines, farther below.  This means that the warming feedback concerning clouds has been considerably underestimated.  And that holding global surface warming to an acceptable level is far more difficult than most scientists thought during 1980-2015.
    The likelihood of catastrophic warming is much higher than we thought.  Earth's carbon budget remaining to keep warming under 2°C is far less than zero.
Legacy carbon in the air is very dangerous and CO2 removal is paramount.

Below are 2 cloud cover trend graphs by Dr. Fry, one by temperature and one by time.

Below are 2 cloudiness graphs from the World Meteorlogical Organization, c. 2009

     The table above shows that, since 1985, cloud cover has been increasing in the tropics and sub-polar regions, especially 10°N to 10° S.  In the sub-tropics and temperate regions (25-45 or 50°, latitude), it has been decreasing.

Ocean Warming due to Plankton Collapse 0616.rtf

Figure 8.2 (in part) from the IPCC 5th Assessment, WGI.

Section Map: Heat