Posted by: erl happ | September 19, 2011

Climate disaster: declining rainfall, rising sea levels

The subject of this post is climate change in the place where I live. The climate has changed in the last sixty years and there is a widespread notion that man is at fault. It’s on the edge of a big desert. Much of the land is salty and the clearing of native vegetation has brought more salt to the surface. There is less rain. Looks like desertification is in process. Many well meaning people point the finger at farmers and we have a ban on the clearing of further native vegetation and a very active forest preservation movement.

In a report at: http://insciences.org/article.php?article_id=8586 we have a description of a paper published in the Journal of Climate, May 2010.

“CSIRO statistician Dr Yun Li and climate physicists Professor Jianping Li and Juan Feng from the Chinese Academy of Sciences remark that since the mid-1970s south-west Western Australia has seen a 15-20 per cent decrease in average winter rainfall, from 323 mm in 1925-1976 to 276 mm from 1976-2003.

South-west WA – a vast area which includes Perth, the Margaret River wine region and the West Australian wheat belt – receives most of its annual rainfall during winter from passing cold fronts and storms. However, since the mid-1970s, the number of storms in the region have decreased leading to less rainfall with the drier conditions being exacerbated due to more high pressure systems entering the area.

Modelling suggests a decrease in mean annual rainfall of 7 per cent and a 14 per cent reduction in surface water runoff in the period 2021 to 2050 relative to the period 1961 to 1990. If current climate trends continue, south-west WA will potentially experience 80 per cent more drought-months by 2070.”

The alarm has also been sounded in relation to sea levels. The increase in sea level on the west coast has been 8 mm per year, about four times that on the east coast. See: http://www.watoday.com.au/environment/sea-levels-could-rise-a-metre-by-2100-20110523-1ezf0.html

Is this just a case of what Leif Svalgaard calls ‘confirmation bias’, namely that ‘you misconstrue to see what you wish’. Is the Commonwealth Scientific and Industrial Research Organization simply projecting on the basis of past experience and a misunderstanding of the science? Is this what is to be expected from a research organization (CSIRO, NASA) funded out of the public purse? Is the notion that this part of the globe is on the way to perdition supportable?

Analysis

The past can be a guide to the future if it informs us as to how the system works. The analysis that follows is based upon observation of historical change. Secondly it is based on an understanding of the elementary laws of gas behavior. Thirdly it is informed by farmers perception that form usually follows function.

All data from http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl

A full screen version of each figure can be seen by simply clicking on that figure.

Figure 1 Sea level pressure by latitude in 1948-57 and 2001-2010. Mb

Since 1948 the global atmosphere has shifted north.

Figure 2 Change in sea level pressure by latitude Mb.

The loss of air pressure at 60-90° south is matched by an increase elsewhere but most particularly at 30-40° south in the latitude of the winds that bring rain to the South West of Western Australia. This is where the fronts should appear. In a ‘front’ air of Antarctic origin lifts moist air of tropical origin causing rain.

Figure 3 Pressure differential between source and sink latitudes for the planetary winds Mb.

The loss of pressure at 60-70° south and the gain at 30-40° south enhances the pressure differential driving the westerly winds with the effect of:

· Enhancing the flow of the circumpolar current, driving water northwards along the western coasts of the southern continents and raising sea levels as it does so and indeed across the global ocean to the north. Sea level falls in the Southern Ocean, the largest expanse of ocean world-wide.

· Reducing the northward penetration of the polar lows that form on the margins of Antarctica that are responsible for frontal rainfall as they meet humid tropical air traveling southwards.

Figure 4

Figure 4 shows the temperature at 10hPa in the polar stratosphere over Antarctica. A dramatic stepwise increase in the winter minimum temperature occurred in 1976-79. Mid 1976 marks the transition from the weak solar cycle 20 to the very active cycle 21. A coincidence?

Figure 5 Change in surface pressure and 10hPa temperature in the region of the southern annular mode of inter-annual climate variation driven by the coupled circulation of stratosphere and troposphere over Antarctica.

The loss of atmospheric mass over Antarctica is documented in Figure 6. In Figure 5 it is seen to be associated with a rise in the temperature of the upper stratosphere all year round but particularly between June and March. It is in July and August that the most severe pressure loss is recorded. These are peak months for winter rainfall in Western Australia.

 Figure 6 Relationship between sea level pressure near Antarctica and in the Indian Ocean to the south west of Western Australia

We see that the episodic loss of atmospheric pressure at 60-70° south is associated with an increase in atmospheric pressure in the Indian Ocean to the south east of Western Australia.

The bigger picture: ENSO

At latitude 60-70° south, ozone is driven into the troposphere by the coupled circulation of the stratosphere and the troposphere over Antarctica. The pattern of pressure anomalies is described as the Southern Annular Mode (SAM) and can be tracked using the Antarctic Oscillation Index (AOI). This phenomenon lies behind the change evident in figures 1 and 2. Notice the decline in Antarctic pressure evident in the brown line in figure 6. The loss of atmospheric pressure over Antarctica relates directly to temperature change in the stratosphere. If the temperature of the upper stratosphere increases it is because there is more ozone in circulation. In consequence atmospheric pressure must fall at 60-70° south.

There is a circularity in the phenomenon. Temperature changes in the stratosphere primarily in response to a change in pressure affecting the rate of feed of NOx from the mesosphere via the night jet. So, a change in pressure raises ozone levels, pressure falls further as the atmosphere warms in response to the presence of ozone, so the night jet is affected and ozone levels increase again, so pressure must fall at 60-70°south. The circulation is so strong and persistent that it produces the lowest atmospheric pressures seen on the entire planet and acts like a bellows shifting the atmosphere to and from Antarctica and indeed all latitudes south of 50° south.

It is plain that the increase in sea level atmospheric pressure in the region to the south and west of Western Australia is due to atmospheric processes causing pressure loss in Antarctica. Loss off pressure indicates a shift in atmospheric mass. The latitude 30-40°south gains atmospheric mass as part of this process.

Figure 7 Southern Oscillation index and sea level pressure in the Indian Ocean to the south-west of Western Australia

In figure 7 we see an interesting relationship between the Southern Oscillation Index (inverted) and sea level pressure to the south-west of Western Australia. Now, remember that the SOI records the changing relationship between surface pressure in a couple of small towns in the Pacific. This change in pressure relations happens to coincide with the warming and cooling of the Pacific and the tropics generally. This is like the canary in the coal mine. The pressure change here represents a sample, and a very tiny sample at that, of the state of the global atmosphere. The SOI is really a relic of 19th Century climate science. I don’t mean to slight Mr Walker, we actually need more like him. He was a big picture man working with very little data.

Notice the stepwise increase in the SOI after 1978, plainly associated with the stepwise increase in stratospheric temperature in Antarctica. Observe the slow recovery in the SOI over the next forty years. In 2011 the SOI has set a new peak (a trough in this graph because the SOI is inverted) in relation to the entire record since 1948. This is La Nina territory. Plainly sea level pressure off Western Australia is due for a fall. When it falls, rainfall will recover and sea level will decline.

Thinking Thinking

This post shows a strong link between Antarctic surface pressure, the ENSO phenomenon, Western Australia rainfall and the level of the sea in relation to the land.

If we are to understand these phenomena we must understand the drivers of Antarctic surface pressure. There is nothing internal to the climate system that can account for what appears to be a 120 year swing in Antarctic surface pressure and the strength of the Westerly winds in the southern hemisphere. As I have illustrated at: http://wattsupwiththat.com/2011/08/20/the-character-of-climate-change-part-3/ cloud cover and sea surface temperature is driven by changes in surface pressure at 60-70° south latitude. Leif Svalgaard tells me that this is a well understood phenomenon. Strangely, I have never seen it explained in print. Perhaps he misconstrued what I was saying. It happens.

If you want to find the place where the stone falls into the water, look for the splash. Examine the ripples spreading out from that point. In the climate pond the biggest splash is in Antarctica. Look again at figure 1 and figure 8 below.

Figure 8 Temperature in the Antarctic stratosphere at 80-90°south

Where in Antarctica is the biggest splash and the associated ripples? The biggest splash is at the top of the stratosphere where the night jet introduces oxides of nitrogen from the mesosphere. Why do the ripples exhibit a less spiky, more organic form at the bottom of the stratosphere than at the top? It’s because of the influence of the coupled circulation that modulates ozone and temperature. It has least influence at the top of the stratosphere where the night jet rules supreme.

Now just in case you have been told that heating of the stratosphere is associated with ‘Planetary Waves’ or ‘tropical convection’ that might be considered to be internal to the system, consider figure 8 but also 9 and 10, the latter showing monthly temperature anomalies as a departure from the 1948-2011 average.

Figure 9 Monthly anomalies at various pressure levels in the Antarctic Stratosphere at 80-90°S 2008-2011

Figure 10 Monthly anomalies at various pressure levels in the Antarctic stratosphere at 80-90°S in 1948-50

It is plain that the temperature of the stratosphere changes first and to the greatest extent at the highest altitude and that change propagates downward. It also appears that temperature at 10hPa tends to jump in November as the Arctic circulation cuts in, the cooling of the Arctic atmosphere and the warming of the Antarctic atmosphere robbing Antarctica of atmospheric mass. The atmosphere is one big pond. The Antarctic represents the strongest circulation. In general you can expect the Antarctic to be deterministic, but here we see the Arctic saying its piece.

And the $64,000 question? What causes the jerks in atmospheric pressure that initiate the transfer of mass from Antarctica and to a lesser extent from the Arctic? We know that the coupled circulation amplifies the process. But what starts it off? This is the question to be resolved if we are to understand and predict climate change. Who do we know that should be able to tell us about the importance of plasma and electromagnetic influences on the  location of the atmosphere?

And here is a $6 question? Why is there less ozone in the southern stratosphere than in the northern stratosphere? Is it partly because it is continually being wasted into the troposphere and attacked by oxides of nitrogen from the mesosphere? Has anyone ever suggested that?

Conclusion

To take this post back to where it started, we can say that the decline in rainfall and increase in sea surface temperature in the south-west of Western Australia is plainly reversible. There is no reason to imagine that the trend of the last forty years should continue.

The sky will not fall.

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Responses

  1. “The increase in sea level on the west coast has been 8 mm per year, about four times that on the east coast. ”

    Don’t people see a problem with this claim? Simple high school physics shows that water remains roughly the same level everywhere. If the sea level rises 8mm in one place, it must rise roughly the same everywhere. If there is a discrepancy, chances are it is not the sea which is rising, it is the land which is sinking. Where I live in N America, the sea has been rising about 6 inches per century, about 200 miles to the NE of me the sea has been rising about 12 inches per century, about 200 miles to the SW the sea has been falling about 3 inches per century. That’s right, falling. In reality it is not the sea which is going up and down, it is the shoreline which is going up and down. This is common knowledge among geologists, but they never speak up for some reason.

    • Hi Klem,
      Where I live the continental plates are much more stable. Since I wrote this post I have discovered that there is a big sea level response to ENSO on the west coast of WA and the 8mm per year resulted from a bit of artful cherry picking on the part of the CSIRO researcher. In reality the long term increase is much smaller.


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