All entries for Wednesday 20 April 2005

April 20, 2005

Global Warming: The facts

In response to recent debate (we started with posing the question to any Labour supporters as to what reasons existed for them to be worthy of getting a vote from anyone, and somehow via the Conservative manifesto ended up on Global Warming), I am publishing some information which may be of interest to many of you.

Firstly, don't call it Global Warming. Global Warming implies an accross the board increase in temperature. The climate is much more complicated than that, and for that reason it's called Climate Change when discussing it here please. But I digress…

Edit Following further discussion, I have realised that this section of analysis is irrelevant for the global warming case due to ice being pure water and seawater being salty and therefore denser A common misconception I'd like to dispell is that melting of polar ice will cause sea levels to rise, flooding great expanses of low-lying land. The poles (at least the north pole) are afloat. Ice is chemically identical to water, it just exists in a different state (solid as opposed to liquid). When ice melts, it forms water. Some physics: objects afloat displace a volume of fluid equal in mass to the object that is afloat. Ice is less dense than water, hence it floats. When ice melts, the volume of water it forms is exactly the same as the volume of water it displaced when it was floating ice, as its density has increased. It's elementary physics really. Go get a cup of water brimfull and some ice cubes if you don't believe me, and see for yourself.

Next, we move on to ice that is on land. Get out a map, and take a look at Greenland. You'll notice that it's probably white. This is because Greenland is actually covered in a layer of ice 4 miles thick. This is melting away, which is causing sea levels to rise. I forget the amount by which they are predicted to rise, but it's a fair few feet. Not enough to drown the world, but enough to alter most coastlines by quite a bit. You might be interested to know, before all you greenies jump up and down in jubilation, that this would be happening whether I go drive my Aston Martin at 150mph or not. This is because the ice is left over from the last ice age, and ocean currents are warming it up and melting it away naturally anyway. There isn't really anything mankind can do about this; our planet is still thawing from the last ice age and that's all there is to it.

Now, your global temperature models. Are you aware of sunspots and solar activity? The sun you see is a very interesting body. It contains about 2×10^50 protons in it, which fuse at its core at the rate of about 4 million tonnes a second, joining to form helium nuclei (and others in a reaction series collectively called the carbon cycle edit: the carbon cycle is much more prevalent in larger stars than our sun, stars the size of our sun and smaller prevalently react in a process called the proton-proton chain reaction. Thanks to Mr Brent for this correction!) by a process we call nuclear fusion. For a big ball of reacting gas, the sun is surprisingly complex with many currents and heat flows and a surprising amount of instability – it's not just on at a steady rate, the sun fluctuates. One of the tell-tale signs of this are hotspots on its surface called sunspots. If you link up sunspot activity to climate variations, you get a surprisingly good correlation. Thus, one of the main drivers for climate variation is in fact our sun and not humanity (hardly surprising when you consider that the earth's surface is being bathed in a constant-ish 1730 watts per sqaure metre of light from the sun). The sunspot cycle varies between 8 and 15 years in length, although it is a relatively short cyclic variation, and solar intensity also varies over much longer periods of time. More on this later.

The main thrust of the argument for man-made Climate Change is that mankind is consuming vast amounts of energy, releasing carbon dioxide into the atmosphere which will cause the climate to change beyond the point of no return. Carbon dioxide is what is termed a "greenhouse gas", that is it has the effect of a blanket in retaining heat in from the earth. Yet CO2 only accounts for around 3% of greenhouse gases in the first place (95% is water vapour, the other 2% methane and other associated gases), and mankind's emissions of CO2 are something in the order of 2% of total CO2 levels I believe, although this last figure may be incorrect (edit: this was incorrect. According to contributors, the figure is closer to 15%. However, 15% of 3% is still a rather miniscule 0.45%). Allow me to dispell the suggestion that the facts support this…

All computer simulations of climate change say that, based on how we understand climate to work, the low layer of air for one to five miles up (the low troposphere), where the radiation is trapped by greenhouse gases, should warm. That low layer of air warming should, in turn, warm the surface. The human-made greenhouse warming component must warm both layers of air, with computer simulations indicating the low troposphere would warm more quickly and to a greater amount than the surface. This has not been supported by scientific facts gathered during the last 10 years. Allow me to present you with two examples of this.

Let's start with the surface temperature records. They are made by thermometers, and go back to about the mid-19th century in locations scattered around the world. For some locations the records go back even further.

Two groups have analyzed these surface temperature records: the Climatic Research Unit in Great Britain, and the NASA Goddard Institute for Space Sciences. They broadly say the same thing: The 19th century was cooler than the 20th century. There may be some disagreement on the exact amount of the warming, but certainly the 20th century was warmer than the 19th.

To see if the 20th-century surface warming is from human activity or not, we begin looking in detail at the surface record. In the 20th century, three trends are easily identified. From 1900 to 1940, the surface warms strongly. From 1940 to about the late 1970s, a slight cooling trend is seen. Then from the late 1970s to the present, warming occurs. Briefly, the surface records show early 20th-century warming, mid-20th-century cooling, and late 20th-century warming.

Most of the increase in the air's concentration of greenhouse gases from human activities—over 80 percent—occurred after the 1940s. That means that the strong early 20th century warming must be largely, if not entirely, natural.

The mid-20th-century cooling can't be a warming response owing to the air's added greenhouse gases. The only portion of this record that could be largely human-made is that of the past few decades. The slope of that trend calculated over the past few decades is about one-tenth of a degree Centigrade per decade.

Now, most all the computer models agree that the human-made warming would be almost linear in fashion. So over a century the extrapolated warming trend expected from continued use of fossil fuels would amount to about 1 degree Centigrade per century. That's what the surface temperature says would be the upper limit.

The surface warming can be concluded as owing to human-made greenhouse gas emissions only if the low troposphere warms, if the computer simulations are accurate. One can have surface warming from a variety of reasons. So the key layer of air to look at is the one-to-five-mile up layer of air.

NASA launched satellites starting in 1979 to measure this layer of air. The satellites look down and record these measurements daily. I've plotted the monthly averages. There are lots of jigs and jags in the data, and they are real.

The air temperature varies not only on a daily basis, on a monthly basis, but also from year to year. A very huge warming spike in 1997–1998 is a strong, natural phenomenon called El Niņo, a warming of the Pacific that in turn warms the air. Because the Pacific is so pervasive in the global average, it raises the temperature. But it doesn't last very long, and after the El Niņo subsided, temperatures fell.

El Niņos are natural and occur every several years. In 1982, an equally strong El Niņo was developing in the Pacific. But then, a volcano erupted. Material lofted by strong volcanic eruptions can temporary cool temperatures. So those two events occurring at nearly the same time meant there was a net cooling just after 1982, instead of an unmasked strong El Niņo-driven pulse of warmth.

El Niņo is part of a system of ocean and air changes called the El Niņo Southern Oscillation, in which the La Niņa phase tends toward cooling. Detailed physical understanding of the El Niņo Southern Oscillation is lacking.

Again, these phenomena are naturally occurring. They have existed for many millennia prior to human-added greenhouse gases in the air.

If you ask the computer to naively draw a linear trend through the data recorded by satellites. This linear trend probably has a bias, an upward bias because of that strong 1997–1998 El Niņo warm pulse. Nonetheless, the fitted trend is: positive four-hundredths of a degree Centigrade per decade.

Now, this is the layer of air sensitive to the human-made warming effect, and the layer that must warm at least as much as the surface according to the computer simulations. Yet, the projected warming from human activities can't be found in the low troposphere in any great degree. The four-hundredths of a degree Centigrade might be entirely due to this El Niņo bias. If the small warming trend in the low troposphere were assumed to be entirely human-caused, the trend is much smaller than forecast by any model. Extrapolated over a century, the observed trend indicates a human-made warming trend no greater than four-tenths of a degree Centigrade.

In contrast, the computer models say this very key layer of air must be warming from human activities. The predictions are that the air must be warming at a rate of approximately a quarter of a degree Centigrade per decade. Comparing what the computer models say should be happening with the actual satellite observations shows a mismatch of around a factor of 6. That is, this layer of air just is not warming the way the computer simulations say it should. There should have been a half a degree Centigrade per decade warming in this layer of air over the period of satellite observations. The human-made warming trend isn't there.

Now, an argument is often made that the measurements made by satellites looking down on this key layer of air are biased, or that the satellites have instrumental problems. NASA researchers worked very hard to make these measurements the best possible, and to correct for any of the deficiencies seen in them. But it's always useful to have an independent set of data, and we have that from NOAA (the National Oceanic and Atmospheric Administration) scientists and from other groups around the world.

Measurements are also made of this layer of air from weather balloons that carry thermometers. Balloons are launched worldwide every day to make the measurements. The balloon data go back to 1957, and importantly, they overlap with the satellite data which began in 1979 and have continued through the present. During the period of overlap, the correlation coefficient between the two data sets, the technical term for how well do these two independent measurements agree, is well over 99 percent. In other words, the satellite data and the balloon data both say that the records reflect the actual change in this layer of air. Again, as with the satellite record, one can recognize short-term natural variations—El Niņo, La Niņa, volcanic eruptions—but one does not see the decades-long human-caused warming trend projected by climate models.

Often, one sees these same data from this key layer of air with a linear trend drawn through them. However, because of bias in the record from a natural phenomenon, it is not appropriate to draw a straight line through the four decades of the temperature record. One must work around the natural phenomenon I'm going to tell you about.

Every 20 to 30 years, the Pacific Ocean changes sharply. The sudden shift is called the Pacific Decadal Oscillation, or PDO, and produces an ocean, air, and wind current shift. Fishermen will notice, for example, migrations of fish species along the West Coast. In 1976–1977 the Pacific Decadal Oscillation shifted, and is labeled the Great Pacific Climate Shift of 1976–1977. As a result, temperatures changed dramatically from their former average (since around 1946), and returned to warmth seen from around 1923 to 1946. So sharp is the shift that the appropriate thing to do is to look for a secular trend (which might be the human-made trend) before 1976–1977, and then after 1976–1977. But drawing a straight line through that natural event should be avoided.

The PDO is natural, because proxy records—of tree growth, for example—detail the oscillation going back several centuries, which is prior to human activities that significantly increase the content of greenhouse gases in the air. And also known from computer simulations is that the human-made warming trend is supposed to grow steadily over decades. So, a shift all at once in 1976–1977 is ruled out by those two reasons. One, it's not what the models project; and two, we see this event before the build-up of human-made greenhouse gases, and it is therefore natural.

The satellite data and the balloon data agree when both records coexist, from 1979 to the present. The balloon record reaches back four decades. Neither record sees a meaningful human-made warming trend.

Now, just remember this one thing from this talk, if nothing else: That layer of air cannot be bypassed; that layer of air must warm if computer model projections are accurate in detailing the human-made warming trend from the air's increased greenhouse gases. But that layer of air is not warming. Thus the human-made effect must be quite small. Additionally, the recent warming trend in the surface record must not owe to the human-made effect. The surface temperature is warming for some other reason, likely natural influences. The argument here, from NASA and NOAA data, is that this layer of air from one to five miles in altitude is not warming the way computer simulations say it must warm in the presence of human activity. Therefore, the human-made effect is small. The surface data must be warming from natural effects, because the human-made warming trend must appear both in the low troposphere and at the surface. All models are in agreement on that.

Now, if the surface data are warming for a natural reason, what might that be? Research teams study changes in the energy output of the sun and its influence on life and the environment of earth. Records of sunspot activity reach back to the days of Galileo, some 400 years ago. Scientists then could project an image of the sun and draw these dark sunspots that were seen through early telescopes. We know sunspots to be areas of intense magnetic activity, and from NASA satellite measurements in the last 20 years, we know that over time periods of decades, when the magnetism of the sun is strong, the energy output of the sun is also more intense. That is, the sun is a little bit brighter when magnetism is high, and the sun is a bit fainter when magnetism is weaker.

The sharp ups and downs in the sunspot record define the familiar 11-year cycle, or sunspot cycle. The period is not exactly 11 years. It varies between eight and 15 years, and there is no good explanation for the cause of the cycle. But I'm not going to look at the short term, but rather the changing sun over decades to centuries.

Over the past half-century, the sun has become very active, and the sun is more active than it has been for 400 years. Therefore, the sun is likely at its brightest in 400 years.

Also noteworthy is a feature called the Maunder Minimum. In the 17th century, the observations of sunspots show extraordinarily low levels of magnetism on the sun, with little or no 11-year cycle. That phase of low solar activity has not been encountered in modern times (although radiocarbon records indicate that a Maunder-minimum episode occurs for a century every several centuries). The 17th-century Maunder Minimum corresponds with the coldest century of the last millennium.

That may not be a coincidence. If the sun's energy output had faded, the earth may have cooled in response to that decrease in the sun's total energy output.

The next step is to look closer at the temperature records on earth, and see if they link to the decadal-to-century changes in the sun's energy output. Climate scientists believe they can reliably reconstruct Northern Hemisphere land temperature data back to, say, the year 1700.

If changes in the energy output of the sun, drawn from the envelope of that activity of changes in the sun's magnetism, are superposed on the reconstructed temperature record, then the two records show a good correlation.

The ups and downs of each record match fairly well. The coincident changes in the sun's changing energy output and temperature records on earth tend to argue that the sun has driven a major portion of the 20th century temperature change. For example, a strong warming in the late 19th century, continuing in the early 20th century, up to the 1940s, seems to follow the sun's energy output changes fairly well.

The mid-20th century cooling, and some of the latter 20th century warming also seem matched to changes in the sun.

To review: The surface warming that should be occurring from human-made actions, which is predicted to be accompanied by low troposphere warming, cannot be found in modern records from balloon and satellite platforms.

Thus, the recent surface warming trend may owe largely to changes in the sun's energy output. QED, W^5 etc…

April 2005

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