Global Average Temperature: Meaningless & Misleading
When most people think of climate change they are really thinking of weather. Specifically the weather where they live. Weather is caused by Earth's climate engine moving heat about, so the two are definitely linked, but is it possible to capture climate in a single number? For years, those alarmed by the prospect of climate change have bandied about a number for Earth's average global temperature, currently given as about 61 degrees F (16°C). But what does that mean? This is why climate alarmists like to talk about the change in global temperature above some past average, starting at some arbitrary time – the real meaning is, well, a bit vague. But if no one can interpret the meaning of Earth's average temperature, what are we to make of a change in that number? As it turns out, Earth's average temperature is a mostly meaningless number, often used to mislead people and susceptible to manipulation for nefarious purposes.
With the climate clown festival that is going on in Paris right now (COP21) people are constantly blathering about stopping climate change at no more than a 2°C rise in temperature. The question a thinking person should immediately ask is “2°C rise above what?” After all, if you live in Death Valley another couple of degrees would probably not be noticed. The mean annual temperature for Death Valley, as reported by the Furnace Creek Weather Station, is 77.2 °F (25.1 °C) with an average high in January of around 67 °F (19 °C) and 116 °F (47 °C) in July. From 1934-1961 the weather station at Cow Creek recorded a mean annual temperature of 77.2 °F (25.1 °C). Do you think another couple of degrees will make a noticeable difference?
Similarly, there are other places on Earth where the temperatures can be extremely hot or extremely cold. The coldest temperature recorded in Antarctica was -89.6°C at Vostok station in 1983. The average winter temperature at the South Pole is about -49°C and temperature seldom goes above zero even in summer. Would a couple of degrees make much of a difference to habitability there? The emperor penguins might find the increase nice, but hardly a game changer.
Where's that 2°C increase they promised us?
The hottest temperature ever recorded on Earth was 70.7°C (159°F), which was taken in the Lut Desert of Iran. Would the difference between 71 and 73 degrees be all that impactful? And remember, this is a rise in average temperature. Would the same amount of rise apply to the extreme highs or the extreme lows? Again using Death Valley as an example, winter daytime temperatures are mild in the low elevations, with cool nights that occasionally reach freezing. Higher elevations are cooler than the low valley. Temperatures drop 3 to 5°F (2 to 3°C) with every thousand vertical feet (approx. 300m). Would it be a catastrophe for temperatures not to drop so low in the high desert? This also brings up the subject of altitude in general.
Is the impact of that dreaded 2°C as fearful at sea level as it is in the mountains? Because, make no mistake, altitude can have a significant impact on temperature. In fact, according to Patrick Moore, “2 degrees C like coming down the Eiffel Tower, or moving from San Francisco across the Bay to Berkeley. Ridiculous.”
As shown in the first figure, different well respected scientific organizations don't even agree on the history of the magic average global temperature. When they talk about temperature “anomaly” – a term climate scientists use because it sounds more scientific and sinister than difference or variability – does adding 2°C apply equally to all temperatures, high, low, and in between, at all locations on Earth?
What most people don't appreciate is that taking an average throws away information. When several numbers are added and reduced to a single number you cannot reverse the process and extract the individual readings from their average. For instance, consider the sequence [2,7,1,8,7]. The average is 5, but there are many other sequences that also average 5: [5,5,5,5,5], [1,9,5,9,1], etc. Just knowing the average does not reflect the sequence of numbers accurately. Also note that a single outlier can bias a sequence of readings – [4,4,4,9,4] averages to 5 as does [6,1,6,6,6] – so not only is variability lost, possible extremes are also smoothed away. Now imagine the numbers are all temperatures.
On December 6th, in Conway, AR, the average high is 49.4°F, the average low 27.4°F, and the average temperature 38.4°F. Right now my computer tells me it is 63°F outside (curse you global warming!), which is in no way predictable from the numbers given. So is this normal? Or is it peculiarly warm for this day of the year? Again, too much information has been lost. Statisticians would say we need to include standard deviation or some higher statistical moments like skew and kurtosis, but that still wont get us back to the original data for this day, let alone predict the day's actual temperature curve.
Similarly, the yearly average high for my home is 71.8°F, the low 49°F, and the average temperature 60.4°F, so the outside temperature is right about average. But I can tell you from experience that we often have days when the temperature does not rise above freezing and also days when the high tops 100°F (37.8°C). Would you expect this from the average yearly temperature? Now imagine combining temperature data from thousands of places around the globe, for every day of the year, and generating an average global temperature—what would that number mean? Not a damned thing.
Now imagine adding 2°C to our useless average global temperature, what does that even mean? Will 2°C affect all areas of the globe equally? Of course not, and there is no descriptive power in the average global temperature number that can give us the true impact of such a change. In truth, we can not tell from that pitiful single number how hot or cold things are or could be on our planet. It's hot in some places and cold in others, yet people live in darn near all of them. From the frozen north to the steamy tropics, humans and other lifeforms inhabit it all.
Another 2°C will make no place on Earth uninhabitable that isn't uninhabitable currently. In fact it might make several places more attractive and comfortable. People flee cold places, like Northern Europe and Canada, in favor of hot places like Majorca and Cancun. The temperature differences involved are much greater than 2°C yet vacationers don't seem to be dropping dead in sunny climes. Not only is average global temperature a meaningless statistic, it is also misleading, because the data used to calculate it has been bastardized by researchers in the name of “science.”
First we have to ask, where does this number come from? According to NOAA, an agency of the US Government, a number of datasets are used to calculate the average global temperature:
Land surface temperatures are available from the Global Historical Climate Network-Monthly (GHCN-M). Sea surface temperatures are determined using the extended reconstructed sea surface temperature (ERSST) analysis. ERSST uses the most recently available International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and statistical methods that allow stable reconstruction using sparse data. The monthly analysis begins January 1854, but due to very sparse data, no global averages are computed before 1880. With more observations after 1880, the signal is stronger and more consistent over time.
Note the mention of both land surface temperatures and sea surface temperatures (SST). These are collected in quite different ways. Then they are “corrected” using statistical methods, more science speak for manipulating the data. The result is something like this:
Now note the reference to “sparse data”, which means actual readings are few and far between in a lot of areas. This is true of both land temperatures and ocean temperatures. For instance, note the huge swathe of South America that has been labeled as “record warmest.” And what is this based on? Here is an image from NOAA itself showing the paucity of data in some areas:
Notice that the same area on this plot shows that there is no data for that area of Brazil! Basically, the “record warmest” temperatures in Brazil and neighboring countries are made up. The fact that they are made up by a computer program makes them no less bogus. The same is true of other areas, like the warm blob shown over Greenland, discredited by other NOAA data. You can find more on this in Paul Homewood's article here.
So we can't even trust this meaningless history of meaningless numbers to even hint at something having to do with climate change. Yet researchers, with vested interest in climate change being a looming crisis, continue to doctor data, making it seem that global temperatures are continuing to rise. Most recently, NOAA researchers lead by Thomas R. Karl, published a new study rather cleverly titled “Possible artifacts of data biases in the recent global surface warming hiatus.” In it they purport to prove that the well accepted 18+ year pause in global temperature rise is just some bad data and that they have been able to fix it. The Abstract:
Much study has been devoted to the possible causes of an apparent decrease in the upward trend of global surface temperatures since 1998, a phenomenon that has been dubbed the global warming “hiatus.” Here, we present an updated global surface temperature analysis that reveals that global trends are higher than those reported by the Intergovernmental Panel on Climate Change, especially in recent decades, and that the central estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a “slowdown” in the increase of global surface temperature.
Much has been written about this latest attempt at temperature legerdemain and I will not repeat it all here, but those interesting can look here for an excellent article on Judith Curry's blog. Here is the essence of what Zeke Hausfather and Kevin Cowtan had to say about reanalyzing Karl et. al's reanalysis:
Significant recent media and political attention has been focused on the new NOAA temperature record, which shows considerably more warming than their prior record during the period from 1998 to present. The main factor behind these changes is the correction in ocean temperatures to account for the transition from ship engine room intake measurement to buoy-based measurements and a calibration of differences across ships using nighttime marine air temperatures (NMAT). Here we seek to evaluate the changes to the NOAA ocean temperature record by constructing a new buoy-only sea surface temperature record. We find that a record using only buoys (and requiring no adjustments) is effectively identical in trend to the new NOAA record and significantly higher than the old one.
What is interesting here is that Hausfather and Cowtan claim that the ship engine intake temps are biased, with respect to the much newer buoy data. Unfortunately, the ship data goes back much farther than the buoy data, comprising much of the historical record. And, as Dr. Curry notes, there is another SST dataset – the OISSTv2 – for the period since the 1980’s. This dataset has higher horizontal resolution owing to the use of satellites, and references satellite and ship observations to the buoys. As Curry notes: “The bottom line seems to be that the NOAA ERSSTv4 1998-2014 trend is about twice as large as the trend for HADSST3 and OISSTv2.” Which is correct? This is where someone shouts “the science is settled!”
Dr. Curry and friends are not alone in questioning the revised NOAA GISS data. Geologist and data computation expert Professor Dr. Friedrich Karl Ewert began looking at the data behind the global warming claims, and especially the datasets of NASA’s Goddard Institute of Space Studies (GISS). He also concluded that the temperature record had been debased, “Massively altered” in the words of one online report.
Perhaps most telling of all, there are other datasets, not dependent on sparse data from scattered temperature stations or disputed sea surface temperature readings from passing vessels. Those records comes from Infra Red satellite observations. Shown below is a comparison of the satellite RSS data and the GISS.
As you can see, between 1979 and 2001, the RSS satellite data increased at virtually the same rate as GISS. Since then, there has been a significant divergence, with GISS depicting a rate of increase essentially unchanged from the earlier period. In contrast RSS (and also UAH, another satellite based history) confirm that, if anything, temperatures have been dropping.
Second, we have to ask where this 2°C number comes from, if scientists are not only muddying the waters with this meaningless temperature number and cooking the books on top of that? What possible scientific justification do they have for claiming that breaking the two degree threshold will render our world uninhabitable? There is none. In the words of a recent Huffington Post article this is the background of the 2°C number:
With the 21st United Nations Convention on Climate Change (COP21) in the news we keep hearing about the need to keep global climate change below a target of two degrees Celsius. However, few people know where this two degrees target comes from. The reason for this is that the two degrees Celsius target is one of the most deliberately muddied topics in the climate change debate. Why would this be? Because this particular target is not a scientific number, but rather a political one.
Note that HuffPo is a collection of green true believers and climate alarmists of the first order.
So there you have it. Average global temperature is a dumbed down, meaningless number only useful for news articles, press releases, and asking for government funding. Knowledgeable scientists, like Roger Pielke Sr., will tell you it has no predictive power. The dreaded 2°C barrier is not some scientifically established tipping point that harkens the end of the world, it is political folderol.
So while such scientific dim bulbs as Barack Obama, John Kerry, and Prince Charles issue stern warning that the apocalypse is neigh even climate alarmists with a grounding in real science like James Hansen admit that 2°C warming limit is “crazy” and not “set on science.” All the climate change sturm und drang issuing from the UN's COP21 conference in Paris is much ado about nothing. My advice to you out there is to ignore all the apocalyptic posturing by the climate alarmists and enjoy the holiday season, whatever the temperature where you are.
Be safe, enjoy the interglacial, and stay skeptical.