What is This Thing Called Climate?

One of the oddest things about the debate (that’s supposedly over) regarding climate is how very little of the discussion is actually about climate. Let’s start by defining what is generally meant by the term. From the OED:

3. a. Condition (of a region or country) in relation to prevailing atmospheric phenomena, as temperature, dryness or humidity, wind, clearness or dullness of sky, etc., esp. as these affect human, animal, or vegetable life.

Originally, climate meant a region, inclination or slope. “The meaning passed in Greek through the senses of ‘slope of ground, e.g. of a mountain range’, the supposed ‘slope or inclination of the earth and sky from the equator to the poles’, ‘the zone or region of the earth occupying a particular elevation on this slope, i.e. lying in the same parallel of latitude’, ‘a clime’, in which sense it was adopted in late Latin.” Aristotle identified three climates, the Northern frigid zone, a Torrid zone to the South and the region between was Temperate as that’s where all the civilised people lived. He also believed that there was a corresponding temperate and frigid zone South of the torrid zone, but that we would never be able to confirm this since, by extrapolation, life could not exist in the torrid zone. Ah, the perils of extrapolation from what is known to what is not yet known!

Moving forward in time a couple of millennia, Russian German climatologist Wladimir Köppen devised  the most widely used climate classification system. He first published his system in 1884 and it underwent several modifications, by himself and his collaborator, Rudolf Geiger. Quoting from the wiki-bloody-pedia:

The system is based on the concept that native vegetation is the best expression of climate. Thus, climate zone boundaries have been selected with vegetation distribution in mind. It combines average annual and monthly temperatures and precipitation, and the seasonality of precipitation.

Thus we can see that there’s no physics (high school, or beyond) in sight, nor are we talking about something global in scope. Climate, for better or worse, is a resolutely local phenomenon. And planet Earth has lots of climates:

File:Koppen World Map (retouched version).png

There’s a high resolution version of this image here that’s suitable for printing on a large format printer, or by tiling on a standard office paper format.

Where The Git lives, the Huon Valley in Southern Tasmania, the climate is Temperate/mesothermal. The Git experiences an average temperature above 10 °C in the warmest months (October to March) and a coldest month average between −3 and 18 °C. Indeed, in the microclimate where The Git resides, temperatures only rarely fall below 0°C.

Fairly obviously, even though the Köppen-Geiger scheme is firmly based in objective measurements, the boundaries are a human invention. Pretty much all vegetation is adaptable to the variations that occur, diurnally and seasonally. The Git’s pear tree suffered from severe frost this spring and it killed all but three blossoms. Nevertheless, the tree will live on and produce many more pears before its eventual demise. COnversely, perhaps perversely, despite the unlikelihood of success, The Git planted out a lemon tree three years ago. One of his neighbours lost ten lemon trees to frost in a couple of decades. The reason for The Git’s success was he planted it immediately adjacent to a 22,000 litre water tank where the water mediated the frost. Putting the water tank where he did, The Git fully acknowledges that he changed the climate and he is not in the least apologetic for this. Or for planting ever so many trees that also changed the climate.

During his many years of growing things, he has never seen any relationship between crop production and Global Average Surface Temperature, anomolies or absolute. He does note that during the 1980s when he was market gardening that there were ever so many field tomatoes grown. When the local climate cooled, we stopped growing field tomatoes because they didn’t ripen before the frost arrived in April. The Git built a greenhouse for his personal tomato needs and The House of Steel is redolent with the wonderful aroma of fresh tomatoes cooking down to a paste for bolognese sauces and gulyas. This year was the first for many that growing field tomatoes would have been possible except that the beginning of the season was extremely cold. When you grow things, you notice weather and climate. When you obtain your information from a supercomputer, not so much.

One thing that’s not obvious from looking at the map above provided so very kindly by the Uinversity of Melbourne is that it is very little different from its predecessors. For sure the Köppen-Geiger climate boundaries change from time to time, but this is not only due to climate changes. There is a vigorous and ongoing debate about where to draw those boundaries. And even though the disagreements are very vigorous, to The Git’s best knowledge nobody involved in these debates feel it in the least bit necessary to label their opponents as deniers, child molesters, or drug pushers.

Following is an image of movements in a Köppen-Geiger boundary in the 20thC from here [The Git apologises for the poor quality of the scan, but it was made in the dim and distant when high-quality scanners were very expensive]:

suckling_mitchell_2000_fig2_3

This is nothing less than a graphic illustration of climate change in the US mid-west during the 20th C. The only “dramatic” change would appear to have been in the 1970s when it was very cold. The 1930s were clearly the warmest period, but mostly the climate was resolutely close to average. One is tempted to say: “Oh nose! The climate’s even more average than we thought!” Of course there were two panics about climate in the 20th C. The first came in the 60s and 70s and was the scare of an imminent ice age. The second, the recent CAGW scare would appear to have less basis than the mid-century scare.

Climatology in the time of Hubert Lamb and Gordon Manley less focussed on the 20th century; they were more interested in learning from the past which is one hell of a lot easier than attempting to learn from a yet-to-be-experienced future. Here’s a graphic from Hubert Lamb:

Climate, vegetation and forest limits in early civilized times

forest_grassland_limits

This map depicts forest and grassland limits throughout North America and Eurasia 2,000 years ago (during the Roman Warm Period) versus today (1960s). Quite clearly the climate over this vast region of the planet was considerably warmer than today. Curiously, the CAGW community insists that should the permafrost region become warm enough to once more grow shrubs and trees, then there will be a massive release of methane from the previously frozen soil and Thermageddon will ensue because of positive feedback. They give no explanation of why this didn’t happen 2,000 years ago.

The reason it didn’t happen last time was probably the same reason it won’t happen in the near future. Field experiments by real climatologists (as distinct from supercomputerists) discovered that when the soil becomes warm enough to support summer shrub growth, the shrubs shade the soil and it remains colder than when it was exposed to full sunlight. It’s called negative feedback.

From the above, we can see that the climates of planet Earth have changed little over the last century. They have done so in the past with great ferocity. Rather than Thermageddon following the Roman Warm Period, there was a great cooling known to historians as the Vandal Minimum. Civilisation collapsed. The Medieval Warm Period that followed saw the true renaissance that built the great cathedrals of Europe and reintroduced Classical learning. This in turn almost collapsed, assaulted by a cooling climate called the Little Ice Age that also saw the Great Plague and the devastation of Europe’s human population. What saved Enlightenment Europe was the widespread adoption of new technologies. And The Git suspects that what will save us from any future decline in local temperature and precipitation is technology. Modern technology, not medieval technology.

Thoughts for the Day

Our greatest glory is not in never falling, but in rising every time we fall. — Confucius

The test of our progress is not whether we add more to the abundance of those who have much it is whether we provide enough for those who have little. — Franklin D. Roosevelt

If we cannot now end our differences, at least we can help make the world safe for diversity. — John F. Kennedy

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