5 green questions, answered as accurately as I know how:

Question 1: Global warming isn’t real is it? I mean we keep reading reports that the planet hasn’t warmed up at all since 1999. Some say it’s cooling down and so on. It’s all a big hoax.

Answer: Scientifically speaking the planet doesn’t really have an “agreed average temperature”. However there are satellite readings, balloon readings and local temperature readings that do not support the assertion that “the average temperature of the planet is on the increase”, and there are even some that suggest the temperature might be cooling. However, let’s try to provide some perspective as to what this means:

  1. The problem here is the focus on the word “warming”, which is misleading. Let’s consider the oceans as a single unit. Think of a glass of water on which a large piece of ice is floating. Do you expect the temperature of the surface of the water to increase, while there’s a big ice cube floating around? Not much perhaps (actually, in the Arctic, an increasing temperature of sea water has been observed since 1995, and recently in the region just north of the Chakchi Sea, waters have been 5° C above average.) The global average surface temperature may not increase. Nevertheless, notice that the ice sheet is shrinking dramatically. That means the ocean is absorbing a very large amount of heat, irrespective of the local temperature readings.
  2. We see the same, but a lesser effect, on land. The permafrost is melting, the glaciers are melting and the snow line on mountains is receding. Heat is being absorbed. There’s also the effect that, where the atmospheric temperature increases, more water evapourates and that takes heat out of the atmosphere.
  3. So the truth is that the planet is measurably absorbing a great deal more heat that it has been doing. This has changed the local climate in many places and the cause is green house gases.

Question 2: But you can’t ascribe these climate changes to human activity, can you? The earth goes through cycles where the temperature rises and then it falls back down again, doesn’t it? Isn’t what’s happening now just the natural order of things?

Answer: The scientific evidence suggests that there’s a roughly 100,000 year cycle of warming and cooling (much of the evidence has been gathered by the analysis of ice cores). The suggested and believable cause of this is that the earth’s orbit oscillates from more circular to more elliptical (the Milankovitch theory). When the orbit is more circular the Earth heats up, the sea level slowly rises and the level of carbon dioxide in the atmosphere increases. Right now we’re coming to the end of a period of rising temperature and sea level. The actual level of carbon dioxide is about 30% higher at these temperature peaks.

Question 3: But of those measurements, the carbon dioxide level is lagging, isn’t it. The carbon dioxide is the effect rather than the cause of the warming, isn’t it?

Answer: There you go, interrupting before I’ve completed the previous question. Never mind, let’s put the two questions together. The phenomenon of green house gases is real. The main green house gas is carbon dioxide, but also there’s methane and water vapor.  Shortwave radiation from the sun hits the earth and (depending on what it hits) some of it is reflected back into the atmosphere as long wave radiation. The green house gases absorb long wave radiation, trapping it in the same way that green house glass traps it. Every time you test a green house gas to see if it does this, it just does it. It never takes a day off.

Estimates suggest that the average global temperature of the Earth would be about -18° C if it weren’t for green house gases (rather than about 15° C). So there seems to be an amplification effect in operation. CO2 is both an effect and a cause of global warming. As the Earth heats up, you get more green house gases, which amplify the temperature rise until it reaches a peak. Currently the global average concentration of carbon dioxide is 387 parts per million and this is rising by an average of 2 ppm per year. This annual  rise is attributable primarily to the 6.3 billion tons of carbon dioxide that human beings release into the atmosphere each year.

Question 4. But the whole process will turn around and stop, just like it did over the past 100,000 year cycles, won’t it?

Answer. Unfortunately no-one knows if it will turn round this time, because this cycle is not the same as the previous cycles. This time we have human beings adding billions of extra tons of carbon dioxide and we have no idea whether the cycle will revert in the way that it did before. The worrying difference is that, according to the evidence, atmospheric carbon dioxide is now higher than it’s ever been in the past 500,000 years. The previous high was about 300 ppm, over 300,000 years ago. It’s now above 380 and rising at 2ppm each year. So, it is likely that the sea level rise and eventual temperature rise will be higher than before.

The Earth is too complex an ecosystem to model accurately. We are in new territory. Nobody knows whether there is a corrective mechanism that will kick in at some point.

Question 5. So we get a little more ice melt and a bit of coastline change, but otherwise what’s the big deal?

Answer. If only it were so. There is an attendant problem caused by the fact that the sea absorbs carbon dioxide. About half of the billions of tons of carbon dioxide we add to the atmosphere get absorbed by the sea. In some ways it’s a useful mechanism because it reduces the green house effect. Unfortunately it raises the Ph level of the sea. What’s happening is that the sea is becoming more and more acidic, as more carbon dioxide is absorbed.

Look at all the coastline of most countries in the world and what you see are sandy beaches. Those sandy beaches are formed from the shells of trillions and trillions of shellfish that have been crumbled up by the waves over millions of years. Well that particular process may come to a full stop. Here’s why:

If the sea continues to absorb carbon dioxide at the current rate then by 2075 all coral reefs will start to die, or have died. (We probably can’t stop this).

By 2300 the sea will be too acidic for shellfish to form shells.

It’s hard to believe, I know, but that’s what the scientific evidence is suggesting. If you want a detailed analysis get hold of the full article called The Darkening Seas from the New Yorker.

What would it mean if there were no shellfish?

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