In December, the all important Climate Change Conference in Bali brought together delegates from 189 countries to forge a deal that would succeed the Kyoto agreement.

The Kyoto Protocol is an international, legally binding agreement to reduce global greenhouse gas emissions. It was agreed in 1997 and came into force in February 2005. Back in 1997, 174 nations ratified the pact to reduce the greenhouse gases emitted by developed countries to at least 5% below 1990 levels by 2008-12. But crucially some of the big nations (notably the US) did not sign up.

Bali was big news. Full of tears and tantrums, strong words and, once again, those infuriating blocking tactics from the US. Throughout the verbal wrangling, one message rang clear: We urgently need a framework which will limit global temperature rises to two degrees or less.

Scientists agree that, while some warming of the atmosphere is now inevitable, we must not let average global temperatures breach the two degree mark. But why two degrees, what’s so special about this figure?

In order to answer this, I thought I might have to read some of the thousands of scientific papers on the subject – not a prospect I relished. But then I realised I might have the answer on my own bookshelves. Last year Mark Lynas, the journalist and author, published a book called ‘Six Degrees – Our Future on a Hotter Planet’. He researched countless research papers in order to piece together what each degree of warming might cause in reality from one degree right up to six degrees. I have this book on my shelves and immediately turned to chapter two (entitled Two Degrees) and found some of the answers…..

Acidified oceans

The oceans are the largest single habitat on the planet. They act as a carbon dioxide sponge soaking up approximately half of the CO2 we emit. However, as the gas is absorbed, the oceans become more acidic. Scientists fear that an increase in acidity could make the oceans toxic to shelled crustaceans – their shells would simply dissolve. If acidity became widespread it could affect the lower food chain with a knock-on effect on the whole food web. Acidity could directly affect the gills of higher organisms such as fish and it could also be the final nail in the coffin for the sensitive coral reefs. Even more worryingly it could affect cocclithophores which remove carbon and whose limestone shells fall to the ocean floor effectively locking away carbon dioxide. Higher acidity might wipe these organisms out, cancelling out this important absorption which would lead to higher CO2 levels in the atmosphere.

Continental heat waves

In the summer of 2003, Europe experienced an unprecedented heat wave which cranked up temperatures right across the continent. Switzerland experienced 41.1 degrees Celsius and the UK topped 100 degrees Fahrenheit for the first time. The record-breaking heat wave took a massive toll on people and the environment. Hundreds of elderly in Paris perished as a direct consequence. The final human death toll across Europe is estimated to have been between 22-35,000 fatalities. It also devastated agriculture with billions of pounds of crops lost. River levels plummeted and algal blooms took hold in rivers and lakes. Alpine glaciers melted at higher rates than ever and permafrost in mountain areas melted. All this devastation and how much above average were temperatures that summer? Just 2.3 degrees Celsius. With a two degree global rise, the prediction is that this ‘freak’ summer of 2003 could be common place by the 2040s and, by then, temperatures in an extreme year would be even higher with serious implications for Europe’s rising population and pressurised wildlife.

The ice caps

You can hardly open a newspaper these days without seeing a melting ice cap. In August 2007, the North-West Passage (the sea route running along the Arctic coastline of Canada), normally barricaded with thick ice, wais virtually ice-free for the first time since records began.

It seems that the melting has already begun. But what about this in a planet that is two degrees hotter? The science is complex and regional warming plays a big part. There’s now much focus on Greenland. It contains enough ice to raise global sea levels by 2 to 5 metres. Scientists think that Greenland’s critical melt temperature is 2.7 degrees of regional warming which might occur in as little as 1.2 degrees of global warming. The debate now rages about the rate of melting once this tipping point is reached. Recent melting has been much faster than scientists expected. Should Greenland go, then most of Miami and Manhattan would be underwater with large parts of London, Bangkok, Bombay and Shanghai also disappearing below the waves. Up to half of humanity could be looking to find a dry home.

There’s more in the book but I’ll leave it there as the message is pretty clear. We need the next stage of the Bali process to be more powerful and precipitate real, urgent action. I hardly dare turn the pages in Mark’s book to see what kind of fate we would face if we fail and we hit a three degree rise.