|The rate of warming increased by a factor of 3.8 from 1992 to 2002 corresponding to the period of "global brightening," and was followed by global cooling.|
*CO2 forcing 1992 - 2002 calculated using the IPCC formula: 5.35*ln(373/356) = .25 Wm-2
Journal of Climate 2012 ; e-View
Measurement Methods Affect the Observed Global Dimming and Brightening
Kaicun Wang,1 Robert E. Dickinson,2 Qian Ma,1 John A. Augustine,3 and Martin Wild4
1 State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, China
Surface incident solar radiation (G) determines our climate and environment. G has been widely observed with a single pyranometer since the late 1950s. Such observations have suggested a widespread decrease between the 1950s and 1980s (“global dimming”), i.e., at a rate of -3.5 W m−2 per decade (or -2% per decade) from 1960 to 1990. Since the early 1990s, the diffuse and direct components of G have been measured independently and a more accurate G was calculated by summing these two measurements. Data from this summation method have suggested that G has increased at a rate of 6.6 W m−2 per decade (3.6% per decade) from 1992 to 2002 (“brightening”) at selected sites. The brightening rates from these studies were also higher than those from a single pyranometer. In this paper, we used 17 years (1995-2011) parallel measurements by the two methods from nearly 50 stations to test whether these two measurement methods of G provide similar long-term trends. Our results show that although measurements of G by the two methods agree very well on a monthly time scale, the long-term trend from 1995 to 2011 determined by the single pyranometer is 2-4 W m−2 per decade less than that from the summation method. This difference of trends in the observed G is statistically significant. The dependence of trends of G on measurement methods uncovered here has an important implication for the widely reported “global dimming” and “brightening” based on datasets collected by different measurement methods, i.e., the dimming might have been less if measured with current summation methods.
"Surface incident solar radiation (G) determines our climate and environment."ReplyDelete
Nonsense. It is the 19.5% of the incident solar radiation that is directly absorbed by the atmosphere that determines the global mean surface temperature, because that directly-absorbed energy maintains the vertical temperature lapse rate structure that is the real "control knob" for surface temperature. Variations in direct surface heating by the Sun, either due to aerosols and clouds, or to variations in latitude, time of day and surface absorptivity, only translates into variations in surface winds and weather. The surface does not heat the atmosphere, globally, as my Venus/Earth temperatures comparison--more than 2 years ago now--simply and definitively demonstrated.
Although I agree with your basic interpretation of the reason for the similarity between Earth and Venus atmospheres I think I must disagree on others of your interpretations.
The decline of temperature with height is a result of declining pressure with height and the initial fund of KE is obtained from solar effects on the ground for a non GHG atmosphere or additionally from direct solar heating of GHGs, clouds and aerosols in the atmosphere where such are present.
The basic distribution of climate zones is set by mass, gravity and insolation but if there are changes in atmospheric composition the climate zones move about as a negative system response to any forcing that seeks to upset the basic configuration set by mass, gravity and insolation.
On Earth, changes in oceanic or solar effects on the atmosphere cause the climate zones to move poleward (less clouds) or equatorward (more clouds) which then alters the amount of energy entering the oceans for a net warming or cooling effect.
Hence the 'dimming' referred to was a result of more equatorward meridional jets during the mid 20th century and the 'brightening' was a result of more poleward zonal jets during the late 20th century warming spell.
We are now back in a dimmer cooling spell as a result of low solar activity.
"industrial emissions played little, if any, role in aerosol-produced cooling between 2000 and 2010"