Q&A: What is some evidence that global warming is real?

I guess there’s two ways of answering the question – we can observe what’s happening around the world or we can look at the science behind global warming.

We know from actual observations taken right around the world that the atmosphere is warming up. Historically we used thermometers sited in weather stations, observatories, airports, universities etc but with the advent of satellite technology we’ve been measuring the temperature of Earth from space for the last 30+ years. Here’s a graph of global temperatures over the last 160 years http://www.flickr.com/photos/trevorandclaire/4981026117/sizes/l/in/photostream/ , to put that into context here’s the graph for the last 2,000 years http://www.globalwarmingart.com/wiki/File:2000_Year_Temperature_Comparison_png

2010 was the hottest year ever recorded and in the last decade we find nine of the ten hottest years on record http://data.giss.nasa.gov/gistemp/

We also know that sea levels have been rising faster than at any time since the end of the last ice-age. At the moment they’re rising by 3.2mm a year. Here’s a graph of recent rises http://www.globalwarmingart.com/wiki/File:Recent_Sea_Level_Rise_png and again, a graph to put it into context http://www.globalwarmingart.com/wiki/File:Holocene_Sea_Level_png .

There has been a very significant increase in the number of adverse weather events – from heatwaves, to droughts, to floods etc. Here for example is a graph produced by the United Nations that shows how the number of floods has significantly increased in recent decades http://maps.grida.no/go/graphic/number-of-flood-events-by-continent-and-decade-since-1950

There is much other evidence of a warming climate from the longer growing seasons, the melting of glacial ice, the expansion of biomes etc.

All these factors, and more, provide us with the evidence that the climate is warming up but what they don’t do is to tell us how or why it’s warming.

To answer these questions we need to turn to science and specifically to quantum mechanics. It’s here, at the molecular level, that we find the reasons as to why warming is occurring.

In a nutshell, the greenhouse gases such as carbon dioxide and methane, vibrate at the same frequency as the wavelength of thermal radiation (infrared). It’s this type of heat energy that becomes trapped in the atmosphere and causes the greenhouse effect. The more of these gases there are the more heat is going to be retained.

We can also trace where these gases come from. For example, carbon dioxide is the primary greenhouse gas that humans emit, this gas has different isotopes (forms). Naturally occurring carbon dioxide has a different ration of isotopes to human produced CO2 and we can measure the proportions of these different isotopes within the atmosphere. This tells us that the CO2 that is now accumulating in the atmosphere has been emitted from human sources.

There’s more about the science side of global warming on this website http://brneurosci.org/co2.html.

It’s worth noting that human induced global warming is one part of a larger picture. We also need to remember that there is a lot of natural warming. And in fact, in terms of the effect on temperatures, the natural warming heat our planet up by 33°C and the human component adds a further 1°C on top of this.

Whilst the human part is small, it is enough to cause quite widespread disruption within the climatic systems.

Natural climate change is something that happens over thousands and millions of years, it allows time for many species to adapt. Indeed, our modern civilisation was largely developed during periods of relatively stable climates. We’ve built cities ad infrastructure in places which were originally safe but are now threatened by rising sea levels. Island nations are having to be evacuated as they become inundated by rising seas.

Agriculture and settlements were located due to their proximity to reliable water supplies, these supplies are being disrupted and already millions of people have been forced to relocate.

It’s only in recent decades that warming has taken off, if it continues into the future – as all indications suggest it will – then the effects on our lifestyles will be quite dramatic and it will become necessary to evacuate many millions of people from coastal areas and to provide aid to up to two billion people in Asia and Africa who will face droughts and famines on an unprecedented scale.