Climate change, as the name suggests, is where the weather changes (e.g. Getting hotter) over long periods of time ranging from tens to millions of years. It has been happening from time to time since before life first began on Earth and will continue long into the future.
The best known climate change was the so-called Ice Age, which finished only a few thousand years ago. At the other end of the temperature scale was the Cretaceous period, 65+ million years ago, famous for the T. Rex and Tricerotops. This was when it was so warm that there were no permenant polar ices caps and sea levels were 100 metres or more higher than they were today! Is it the same as global warming?
Not quite. Climate change includes global cooling (Such as the Ice Age) as well as global warming (like the Cretaceous).
What is the difference between weather & climate?
Weather is what you get over short periods of time ranging from minutes to a few years. Climate is what happens over longer periods. Whilst weather can vary dramatically, even to the point of extreme events like hurricanes and floods, in the long run it generally evens out (= climate). When it doesn't, then climate change may be going on.
What is the greenhouse effect and how does it relate to climate change?
This is where the Earth's atmosphere acts like a greenhouse and traps heat, preventing it radiating out into Space. We depend on this effect because, if it weren't there, the global temperature would be 30 degrees centigrade cooler!
The reason heat is trapped is because of so-called greenhouse gases (or GHGs). These include water vapour, CO2, methane, Nitrous Oxide, and even ozone. These are all known to absorb and radiate heat and together they form a kind of blanket around our world.
So what's all the fuss about?
Whilst the greenhouse effect is of huge benefit to us all, perhaps even to life itself, it can also have a sinister side: If, for some reason, the amount of GHGs in the atmosphere were to start growing, the greenhouse effect could get out of hand and overheat the planet. An extreme version of this has happened on Venus where the thick blanket of GHGs has raised the temperature there to around 480 degrees C, way above what it should be even though it's closer to the Sun.
Thankfully, we're not going to turn into Venus anytime soon, but climate scientists are nonetheless concerned. This is where the current climate change controversy comes in: On the one hand climatologists are saying global warming has started and is "very likely" due to us; on the other, you have the sceptics who say that either warming isn't happening, or the warming isn't due to us.
More about GHGs here.
More about the greenhouse effect here.
So who's right?
I might be considered biased here, but I have made a point of finding out about both sides of the argument.
Sceptics who say climate change isn't happening, base their views on the claims that a) ground based temperature measurements are flawed, or b) the data has been manipulated to give the results scientists want.
a) The flawed temperature measurement argument goes like this: Many of the weather stations taking these temperatures have been swallowed up by cities and are therefore subject to the urban heat island effect , which would tend to make things seem warmer. However, these claims have been looked into and shown to be wrong. Most of the urban stations are still found in open areas like parks so they aren't effected. And when urban station readings are compared with rural ones, they show the same rise in temperature. Then there are sea-surface temperatures, marine air temperatures, tropospheric temperatures, surface humidity, ocean heat content, spring snow cover, sea-level and others which all show a consistent warming world picture.
b) In the face of all these different ways of showing that the climate is warming, the claim that the many different groups of scientists are somehow manipulating this mass of data, seems odd to say the least. It also assumes that somehow hundreds of scientists are conspiring to mislead the public, the media, and governments alike. I don't think so.
Sceptics who say that humans aren't causing the warming say that it is part of a natural cycle, that CO2 is too insignificant, and that our contribution to GHGs is too small to make a difference.
The Earth's climate is subject to numerous cycles, the most well known of which is El Nino, but current rapid rise in temperature is like nothing we've seen for thousands of years. Furthermore, none of the known, natural ways of increasing the temperature seem responsible. The only dramatic changes that are known to be going on are down to us.
The proportion of CO2 in the atmosphere is very small (a tiny fraction of 1%) and is still small when compared to other GHGs. However, it's effect is comparatively great: Between 9 - 26% of the total greenhouse effect. When you consider that the amount of CO2 in the atmosphere is known to have increased by more than 30% since the start of the Industrial Revolution, you can see why it's being seen as the 'smoking gun'.
So is this increase in CO2 due to human activity (e.g. cutting down forests, and burning oil, gas, and coal)? Well, natural sources of CO2 are 20 times what we produce. However, prior to the Industrial Revolution, the environment had found a balance, taking out as much CO2 from the system as was being put in. Now, however, it seems we may have over-loaded the system, as only around 50% of our contribution is being removed. The rest is added to the atmosphere.
It is that apparently minor, extra contribution that is making all the difference. Glaciers are receeding, polar ice caps are thinning, sea levels are rising, and temperature records are being beaten. That's all down to us and it's time we did something about it.
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