Climate changes

The basics are that the climate is not a static thing, and it has been changing throughout the approximately 4,000,000,000 years the planet has existed.

There are four main camps in the climate change debate, and they use graphs with four different time scales. Despite the name-calling and hysteria surrounding the debate, ALL FOUR CAMPS ARE ESSENTIALLY CORRECT!

1. The last couple of hundred years scale - the anthropogenic global warming (AGW) camp
2. The last few thousand years scale - the climate changes all the time (CCAT) camp
3. The last 450 thousand years scale - the ice age is coming (IAC) camp
4. The last 3,000 million years scale - we're living in an ice age (LIA) camp

(Please refer to my website: http://theclimatechanges.com for graphs and more information about the changing climate.

The last couple of hundred years

The last couple of hundred years have seen an increase in global average temperature, which the AGW camp says is "alarming". The more hysterical claim rising temperatures will destroy the planet, and cause an end to life as we know it.

There seems little dispute (but there is some) that the climate is changing and that global average temperatures are warming up. As the planet as a whole warms, the sea currents change, the amount of water vapour in the air increases, and these changes can cause more extreme weather events such as floods, droughts, blizzards, and so on.

The AGW camp say it's all our fault and if we just stop spewing out CO2 and cutting down forests the climate will stop changing and everything will be fine. These are good things to do because the alternatives are generally more sustainable, and there's little doubt that our CO2 emissions are adding to global warming, but would the climate really stop changing? It never has before.

There are a few problems with the AGW camp's arguments, and with their terminology. Firstly, CO2 is not a pollutant, and greenhouse gases have always been there, and almost all CO2 in the atmosphere is from causes other than human activities. Without CO2 there would be no life on earth. Not only is CO2 used by plants in photosynthesis, which is basic to all life, but CO2's presence in the atmosphere keeps the earth warm enough for us to live on. The second problem with the AGW debate is that global warming has happened before, many times, and it's been much hotter than it is now, and it had nothing to do with human activity, and the planet has survived just fine. A third is that there's a lag between warming and CO2 levels, with CO2 levels lagging behind warming by around 800 years.

None of these problems mean we shouldn't reduce emissions or stop cutting down forests, because there's little doubt we are probably adding to global warming, and reducing emissions could reduce the temperature rise. And that's important because even though it's all happened before, it's different now because there are 6,800,000,000 humans on earth, and they can't be supported if the temperature rises too high. Droughts, floods and sea level rises will displace hundreds of millions and probably tens of millions will starve. Reducing emissions also means adopting more sustainable technologies.

The last few thousand years

The last few thousand years scale is chosen because it includes the Medieval Warm Period (MWP) and the Little Ice Age (LIA), and the CCAT camp want to show that the climate changes all the time, and that previous warming trends have had nothing to do with human activity. They will often choose to go back to the end of the last glaciation (colloquially called the last ice age) so the Holocene Maximum and Younger Dryas are included as well (YD ended around 8,000 years ago). In that period global warming proceeded at 2 degrees per decade (as opposed to 0.1 degrees now), and the temperature rose by 10 degrees in only 50 years.

The CCAT camp is also correct. The climate does change all the time, and there have been periods of rapid warming that had nothing whatever to do with human activity.

The last 450,000 years

The last 450,000 years scale is used because this is how far the ice core samples go back (since before that there was no ice). This scale shows on a bigger time scale that the climate goes through cycles of glaciation and global warming. Glaciations go for around 100,000 years, and global warming goes for around 10-12,000 years.

What's noticeable here is that we're at the end of an inter-glacial warm period (although the graph calls the glaciations ice ages, which is the colloquial term rather than the scientific term. It's also been much hotter than it is today. The temperature also appears to have levelled off over the last couple of thousand years or so. This relative stability has of course allowed agriculture to expand, and our population to explode, but you don't need me to tell you what is inevitably coming next. The question is when will the next glaciation be? It looks like it's imminent but on this scale, it means possibly sometime in the next 1,000 years or so.

So the IAC camp is also correct.

The last 3,000,000,000 years

The earth has been around for approximately four billion years, and geologists can estimate temperatures in the distant past from rocks. Most of the rocks older than three billion years have weathered away, but three billion years is a pretty long time really. What these data show is that we are actually living in an ice age, and most of the time it's been 22 degrees C, which is about 8 degrees hotter than it is today.

There are peat bogs in Siberia and Alaska, and the remains of tropical rainforests in places like Scotland. We are actually living in a very cold, CO2 impoverished time. The planet has survived much hotter temperatures than the current global warming is likely to throw at us. So the planet is in no trouble, and in fact more CO2 and warmer temperatures mean more plants can grow, not less.

So the LIA camp is also correct.