Firstly, many thanks to Marcus Badger from the University of Bristol who delivered an extremely interesting and informative talk. Secondly, thanks to James for organising the speaker and to Sally for organising the refreshments – and to everyone who came, it was great to see lots of new faces.
I made a few notes so hope they’re accurate and reflect the evening’s presentation which was about what the past can tell us about our future. Marcus was great at explaining the science behind it all – I just hope I’ve understood it well enough to pass on…
Much of the talk was based around what scientists know, what they probably know, what they think they know… and what they have no idea about, which gave great clarity and force to what was said. So, what is known was demonstrated through evidence such as the ice or mud cores revealing different levels of CO2 or methane back through thousands or millions of years.
The magnitude of change in CO2 levels was the main topic of the evening: there are now 396 parts per million, compared with 320 in 1960; 275 in a non glacier period and 175 in an ice age, ie the additional 100 parts of CO2 is the same change as coming out of an ice age, with the additional CO2 coming from oil, gas, coal and cement (known because of the decline in radio carbon around the world which indicates the CO2 comes from dead carbon ie fossil fuels). So in this case, scientists know increasing levels of CO2 are coming from fossil fuels.
Increasing methane levels are probably because of a number of reasons, including rice and ruminant agriculture; gas pipe leakage; and thawing of the permafrost.
The oceans absorb much of the CO2, making the water more acidic, which may in time have an effect on sea life, particularly corals as reefs become bleached and dissolve. Some corals seem to be coping better than others so there is no clear picture yet, but they are a primary element of the food chain so what happens to them will impact elsewhere.
Another ‘known’: increased levels of CO2 are linked to increased temperatures, although there are other factors contributing to global warming: the sun, the earth’s orbit, albedo (the reflective nature of surfaces eg ice sheets are white and shiny and therefore reflective, oceans are dark and matt and not reflective), other greenhouse gases (inc water vapour and methane).
Global temperatures have increased by 0.6 degrees over the last century: scientists’ predictions of what may happen in the future are based on various models. For example, one model maps the changes in CO2 and temperature since the C19th and shows that they match. Therefore based on the same principle, if temperatures continue to increase in line with CO2, this should lead to a 4 degree increase in temperature by the end of this century – which would be catastrophic for most people in the world unless they have the resources to mitigate the changes, so most impact would fall on 2nd or 3rd world countries.
One of the major implications of increased temperatures is rising sea levels, and these changes have been tracked since the 1880s, alongside melting glaciers and arctic sea ice. (recommendation to see ‘Chasing Ice’ film). Some of these changes are happening much faster than expected, in particular Greenland losing its ice mass which will have a major impact on sea levels.
Another ‘known’: increased temperatures lead to more hurricanes and more intense hurricanes because of warmer oceans, although it’s not possible to say any one hurricane was caused by climate change.
As well as ice levels building up over time revealing changing levels of CO2, ocean sediments also build up and form an archive of time with datable layers formed from hundreds of meters of sediment, which have been studied from 1966 onwards, showing CO2 levels over 45 million years. At that time the earth was extremely hot with no ice caps and CO2 levels were also very high – so today’s levels are by no means the highest levels ever, but the changes are happening very quickly giving species little time to adapt. Today’s 396 ppm CO2 is the highest level in the last 3 million years. By the end of this century, CO2 levels will be the same as 25 million years ago. If we do nothing to reduce carbon emissions, scientists think that when CO2 levels and temperature eventually correlate and stabilise, 396 ppm may be the equivalent of a sea rise of 24m leaving upper Clevedon as an island … (google earth have a sea level rising programme if you want to see the impact…)
However, things are moving much faster than expected five years ago, so the picture is unclear. Marcus suggested that the best way to stop climate change is to stop emitting CO2, but as our economies are hydrocarbon based we will need to rely on human flexibility and innovation to provide the answers, and that individuals need to be role models to show others that a low-carbon, less consumerist lifestyle isn’t as difficult as it may appear… With oil companies expert at making money, it isn’t beyond hope that they could change their focus to making money from new ‘green’ industries.