Chief hydrologist on Judith Curry blog
- Chief Hydrologist | February 9, 2011 at 9:46 pm |
‘We have an observed period between 1977 and 1998, during which most of the observed warming of the past 50 years has occurred.’
Yes – no matter what metric you use or statistics are spun – this seems to be a statement of indisputable fact.
‘The sea surface temperature increased as the marine low-level clouds decreased.’
I have been called on the low-level stratiform cloud with some validity. Zhu Ping et al certainly talk about low level cloud. Clement and Burgman talk about total cloud. Total cloud follows the pattern described – and the satellite measurements confirm the energy implications of changing cloud.
The short explanation is that the Pacific trade winds set up conditions for a La Niña. Trade winds, south-easterly in the Southern Hemisphere and north-easterly in the Northern Hemisphere, pile up warm surface water against Australia and Indonesia. Water vapour rises in the western Pacific creating low pressure cells that strengthen the trade winds piling yet more warm water up in the western Pacific. Cool, subsurface water rises in the eastern Pacific and spreads westward. At some point the trade winds falter and warm water spreads out westward across the Pacific.
Warm oceans conditions in an El Niño are associated with reduced cloud cover – reduced cloud lets in more of the Sun’s energy warming oceans and atmosphere.
‘Satellite data show us that most of the reduction in outgoing radiation over this period occurred in the SW band from a decrease in reflected incoming radiation and very little in the LW band from the GH effect’
There is an enhanced greenhouse effect. It can be seen in IR spectral analysis. For instance – take an IR snapshot in 1979 and 2000 and compare emissions in the greenhouse gas bandwidths. Observationally certain.
But the longitudinal record (1984 to the late 1990′s) shows an increase in heat emitted by the planet – because energy in conserved that is heat lost from the planet. At the same time there was a stronger warming effect in the visible spectrum. Less light reflected from less cloud. The net effect was warming. Again, based on pure observation. It doesn’t rely on absolute values – which are a bit problematical – and the trends are valid when estimates of ‘stability uncertainty’ are included.
‘Prior to this period of warming we had a prolonged period of cooling, which coincided with a period of La Niña events.’
The well known mid century slump that has a partial explanation in sulphates. Sulphates are unlikely to the entire explanation because of Arctic amplification (http://www.lanl.gov/source/orgs/ees/ees14/pdfs/09Chlylek.pdf)
Theres is no reason to suppose that sulphates are responsible for the large amplification of the signal in the Arctic. It coincides exactly with a cool La Nina dominated Pacific Ocean multi-decadal mode.
‘After the period of cooling, i.e. most recently, we have observed slight cooling, again with a shift to La Niña’
The multi-decadal pattern includes the PDO. The physical signals are a bit vague – such that NASA called it in 2008. Bloody physicists. This is a biological phenomenon as well with nutrient rich water rising in the Eastern Pacific. There is little doubt from biological indicators – chinook salmon in North American streams in numbers not seen since the 1970′s, sardines in Monterey Bay where they haven’t been seen in numbers for decades, phytoplankton (the base of the food chain) in the equatorial Pacific returned in abundance again not seen since the 1970′s – show that the shift occurred after 1998.
The CERES record is quite inconclusive on warming or cooling in the past decade. I would suggest very moderate cooling – but only because solar irradiance fell to a solar cycle minimum in 2008.
As the Pacific multi-decadal mode involves modulation of the frequency and intensity of ENSO – the current super La Niña should be a taste of things to come.
‘A test for the hypothesis will be the next decade or two: if increased low level clouds continue to contribute to cooling at the same time as La Niña dominates, this will confirm the correlation’
Again, I will have to get back to you on low cloud. The CERES data from 2000 on the other hand will be definitive sometime in the future. Who was it who said that prediction is very difficult – especially if it is about the future.
We seem to have both a plausible mechanism and experimental proof in the data from the satellite platforms that shows that something is amiss in climate science .
My message that I keep giving to our alarmist friends is, even if we just keep drifting along for another decade, this will make the politics of carbon reduction impossible unless we very quickly find another narrative. This is difficult but necessary and may require a bit of groveling and backpedaling. What price they are right and I am wrong and do they want to take that all in gamble?
‘But the main “take home” seems to be that we are in a chaotic climate system, which appears to be closely correlated to ENSO oscillations, with a possible underlying warming trend from AGW.’
The skeptics hate me for this. But the other foundational error in climate science is in the assumption that weather is an ‘initial value problem’ and climate a ‘boundary value problem’. The distinction sees weather as ‘chaotic’ and climate as the ‘statistics of weather’. The new scientific consensus is that both weather and climate are chaotic. For example, the British Royal Society in their recent climate science summary discussed internal climate variability as a result of climate being an example of a chaotic system in theoretical physics (Bart thinks they should have got there decades ago and perhaps so – I can’t gloat because essentially I still am nearly as clueless as anyone).
While this may seem to be a quibble on a minor point to many – it is in fact central to consideration of climate predictability and climate risk. In a chaotic climate – predictability and risk are two sides of a coin. Climate predictions can only be made in terms of probabilities and a range of climate risk from anthropogenic greenhouse gas emissions is mathematically certain as a result of those same probabilities. If we can’t predict that abrupt and violent climate change won’t happen – it is quite a quandary.