Whenever I look at the Mann Hockey Stick reconstruction of past climate I am ever awestruck by the small amount of temperature change depicted during the first 900 years of the chart. It just doesn’t seem possible. Very nearly no climate variation for hundreds of years, and then presto, lots of variation.
I often wonder what the powers that be at the UN must have been thinking in 2002 when they made the Mann Hockey Stick Graph the new climate standard. A new, untested theory with multiple indications of probable sloppy mathematics; science is not supposed to work that way. It is still around, and still defended vigorously by many in the climate community.
Here is a copy of an image of the 1000 year Mann graph I pulled from a Skeptical Science web post defending Mann’s work:
Climate variation shown before 1950 is, according to the IPCC, mostly natural climate variation. The increase in variation started at about the same time direct measurement replaced indirect measurement. This chart begins using direct measurement in 1902. Interesting….and odd too.
The UK’s East Anglia Climate Research Unit (CRU) has direct measurement data that begins in 1860. NOAA data dates back to 1880. Why start in 1902? And when does the data begin to look like a hockey stick? Hmmm…1900…enough said.
Zoom in on 1815 if you can. A very small decrease in temperature that had been trending downward since about 1775, stops in about 1830. The net change for the entire period was only a bit over -0.1 degree C. Something is wrong. This should be a time of spectacular natural change. The very small, nearly no change shown makes no sense. Why? Mt. Tambora.
Mt. Tambora is a 9354 ft. mountain in Indonesia. It used to be over 14,000 feet tall. One day in April of 1815, the top 5000 feet went away. Imagine if you can, an eruption 150 times larger than the Mount St. Helens eruption of May 18,1980. Tambora is the largest volcanic eruption in recorded history. The eruption has been estimated to be 10 times the size of the Mt. Pinatubo eruption of 1991. Mt. Pinatubo has been credited with cooling the world’s weather by about 0.5 degree C for 2 years.
Tambora was and still is a big deal. 1815 has been called the year without a summer because the air pollution from the eruption made the world a darker and colder place. Five degrees F. colder or so says a USA Today article. The winter of 1815-16 was a spectacularly cold one all over the world.
An eruption that big should have caused a significant temporary change in the world climate that would have lasted for several years, perhaps longer. Look at the Mann Chart. Nothing. Where did the Mt. Tambora impact go?
Skeptical Science provided the following temperature reconstruction as a defense of the Mann work on their web site. The two studies supposedly confirm each other. The new study has an advantage over the Mann work in that it covers a shorter period of time making it easier to read:
Where is the -3 degree C blip in 1815? Nothing, Nada, Zip? Whaaaaat? A smaller but significant eruption in 1883, Krakatoa, is not visible either. Another significant eruption, at Huaynaputina, in 1600 fails to make the chart. Too small to be detected I suppose. Changes in the 20th century are here, there and everywhere. This inconsistency has never made sense to me.
The Mann reconstruction is a Northern Hemisphere reconstruction of a 1000 year period. At it’s beginning settlers in Greenland grew hay and their diet was 80% farm animal based including cattle. Yep cattle in Greenland. 400 years later, most settlers were gone. The survivors ate primarily whatever they could harvest from the sea. And all the while the world only cooled 0.1 degree C? I don’t think so.
20th century warming 7 or 8 times that much?
Most warming before 1950, and some warming since 1950 is presumed to be natural climate variation. No natural climate variation for centuries and then magically lots!? AND it coincided with a change in the data source. Come on guys. Get REAL.
I don’t doubt that the world has warmed, but I do believe that all the data before 1902 in the Mann reconstruction is a guess….a wild ass guess. Mann has claimed the entire Medieval Warming Period was a regional event or so he is cited in a Scientific American article published in 2005. I don’t buy it. Greenland was warm for hundreds of years. Records all over Northern Europe support the notion that the warmer weather was widespread and lasted for hundreds of years.
Before the Mann study it was widely believed that the Medieval Warming Period was warmer than Mann claims. Simple charts were included in UN studies as this one that was featured in the first study published by the IPCC in 1992..
The Third Assessment of Climate (TAR), published by the IPCC in 2002 featured a new world order, the Mann chart. Magically, the Medieval Warming Period disappeared.
Now consider this.
The scale for measuring volcanoes is called the Volcanic Explosivity Index. It goes up to 8. Mt. St. Helen’s was a 5, Mt. Pinatubo, Huaynaputina and Krakatoa were in category 6. Mt. Tambora was a 7. The average 7 is 100 times larger than the average 5.
Some 26,500 years ago a big chunk of New Zealand went away in the world’s most recent category 8 eruption at Taupo Volcano. A category 8 eruption is on average 10 times larger than a category 7. Imagine what that must have done to the ecosystem. Now there’s a tipping point, Nature’s tipping point.
This happened during an ice age cold spell. Wow.
Now consider this.
Taupo was a boringly average category 8. 75,000 years ago, plus or minus 5000 years, the Indonesian area blessed us with Toba, the largest category 8 known to man. This beast was the equivalent of 3 Taupo’s and is suspected of starting a 1,000 year cooling period.
I’ll bet you right now that science will discover more significant volcanic activity. Some of that activity will have global climate implications. Who knows how many more will be discovered that have the ability to impact climate as we look back in time?