Musings on comments in the media and blogosphere ...

I can change your mind about Climate Change 1

Anna Rose : We have already seen ¾ degree warming…
Richard Lindzen: We should have seen 3 according to the models


A throwaway comment, by Lindzen, but extremely important. If the models are over predicting the observed temperature trend by a factor of four (as Lindzen claims) then they would indeed be woefully deficient, particularly given that by their nature they should be good at simulating temperature changes.
But no model used in the IPCC AR4 (or models currently available for AR5) simulate an observed warming of anywhere near 3 degrees. They all get it about right: an average of about ¾ of a degree over the last century or so (see figure). Anyone can check this out for themselves by downloading the raw model output from PCMDI (free and open acess to everything). Given a climate sensitivity of about 3C for a doubling of CO2 (which is what on average the models have) a 30% increase in CO2 (as we’ve observed) would produce a equilibrium warming of 1C and given that it takes some time to reach equilibrium we would expect an increase somewhat smaller than 1C – exactly what the models simulate.

So I can only come up with two possible explanations for Lindzen’s demonstrably wrong remark:

  1. As a climate scientist, who frequently argues that models are deficient, he is negligently ignorant of one of the fundamental results from the climate models.
  2. He is knowingly misleading people in a forum where the questioners don’t have the background knowledge to know that his response is completely wrong. And even when the error is discovered it will never undo the fallacy that was broadcast to millions of people.

 

I can change your mind about Climate Change 2

Another oft spouted reason why CO2 cant be important, was mentioned by Clive Palmer a number of times on the QandA program: man-made CO2 is only 3% of the total amount emitted each year, the remaining 97% is natural.
This is actually more or less true. During winter the ocean and land surface release about 190Gt of carbon into the atmosphere. If you compare this with the amount emitted as a result of fossil fuel burning and land use change, about 8Gt of carbon, we can see where Clive gets his numbers (8/(190+8)=4%).  Trouble is the natural flux emitted each winter is absorbed again in the summer – the 190Gt gets removed from the atmosphere again and all that’s left over is the 8Gt that humans emitted*.
Its like money going in and out of a bank account. Say we are paid $100 each week that we deposit in our bank, but then the sum of all our bills also comes to $100 each week. 100 in, 100 out and nothing changes in our bank account. If we get a raise of $3 a week, the extra money going in is only 3% of the total, but every week our savings increase by $3. Wait long enough and we can accumulate a fortune!

This is exactly what we see in the measurements. In any given year the rise due to natural emissions is much larger than any rise due to human emissions. But that large rise is removed again with only a small amount left over. So each year the total goes up a little bit, so that now we have CO2 levels that are higher than at any time in at least a million years.

That Clive Palmers comment is wrong is trivially obvious if we look at the CO2 observations (see figure) - while the seasonal changes dominate human emissions in any year, over multiple decades the accumulated human emissions make a huge difference.

* there is a slight complication to the story. Because of the rising average CO2 in the atmosphere the amount of CO2 reabsorbed each year by the atmosphere and ocean is slightly more than the amount that is emitted naturally. As such the ocean and the atmosphere actually slow the rate of CO2 increase by about 30% each year compared to a straight forward 8Gt increase each year. This is called a negative feedback (on the land its associates with a process called carbon fertilisation). In the bank account example, its analogous to our bills rising to $101 when our salary is increased to $103.

CLIMATE CHANGE & FISHERIES

Pacific Islanders are heavily reliant on the oceans bounty for food security, livelihoods and economic growth. Over the next 25 years the population of the tropical Pacific is set to rise by 50%. This will put enormous strain on marine resources. At the same time Global Warming will significantly modify the ocean environment that supports vital fisheries and aquaculture.
In this project we examine the the Tropical Pacific might change in the future and how this will affect marine species.

http://www.spc.int/climate-change/fisheries/assessment/

CLIMATE CHANGE IN THE TROPICAL PACIFIC

The climate of tropical Pacific Island is dominated by the ocean. Changes to the ocean will therefore have major implications for the region. A collaboration between BOM, CSIRO, Australian Universities and Island stakeholders, under the banner of the PCCSP, are putting together a major new analysis of Climate Change in the Pacific.

http://www.cawcr.gov.au/projects/PCCSP/publications.html

OCEANS DRIVING AUSTRALIAN RAINFALL

Subtle changes to ocean temperature can control regional rainfall patterns, as dramatically demonstrated by the the La Nina induced Queensland floods. We have shown that changes in the Indian Ocean are often as important as those in the Pacific Ocean (associated with ENSO) for rainfall changes in western and eastern Australia and in other Indian Ocean rim countries.
In particular Indian Ocean variability is strongly implicated in causing the worst historical droughts over southeastern Australia

MONSOON AND MODOKI

In recent years the signature of El Ninos seems to have changed, Instead of causing broad scale warming in the eastern Pacific El Ninos now often produce warming confined to the central Pacific - these are termed El Nino Modoki. Our work has shown that during Modoki events the Australian monsoon doesn't follow its normal progression - instead it starts late, terminates early and becomes more intense

Recent work also shows that the Indian monsoon that is normally extra strong during El Nino years can be weakened by the Indian Ocean Dipole

OYSTERS & CARBON SEQUESTRATION

Carbon credits wil be a lucrative extra income to some businesses in the future. But does growing oysters remove carbon from the atmosphere as some have claims?

Ocean chemistry means that the growth of oyster shell actually increases dissolved CO2 concentration and so slows the sequestration of CO2 from the atmosphere (read more)