Six degrees of global warming a bad thing?

Many abstractions surround climate change. A ‘two degree target for global temperature rise’ is one of them. Why would three, four, five or even six degrees celsius of global warming be a bad thing? This post is based on the book Six Degrees by Mark Lynas.

One degree
One degree
two degrees
Two degrees

One Degree

OCEAN Increase in hurricane activity due to warmer oceans. Uptake of excess CO2 makes the oceans acidic causing marine life to die-off.

FOREST Deforestation for agriculture, logging and fuel causing more warming. Less trees means less CO2 uptake and burning forest releases more CO2.

PERMAFROST Permafrost, mountain glacier and snowpack melt causing lake drainage and a downstream water supply shortage.

SEA ICE Arctic ice melt cause more warming. Ice reflects 80% of the Sun’s heat whereas dark ocean absorbs 95% of the heat.

Two Degrees

DROUGHT Crippling droughts cause crop losses. International food price has to be stabilised, to prevent famines.

FLOODS More warmth leads to more water vapour, leading to more intens rainfall. Monsoon increase in South Asia leads to mass human migration.

FOREST Heatwaves in Europe are common. Forest fires occur as far north as the Baltic coast.

PERMAFROST Melt rate doubles, soil starts to release carbon. Greenland is on its way to melt completely causing sea level rise of 7 metres (takes 140 years).

SEA LEVEL Storm surges and sea level rise (expansion of warmer oceans, melted ice sheets) affects the homes of millions as the sea invades low lying cities.

Three Degrees

DROUGHT Parts of Africa and Australia are beyond human adaptation. Drought will be permanent in the sub-tropics and Central America.

MANKIND Population transfers are bigger than anything seen in the history of mankind. Will lead to conflict and international wars.

FOREST Amazon dries out completely. Wild fires in South America cause intense air pollution and heat. The smoke will blot out the sun.

VEGETATION Soil and vegetation start to release C02 rather than absorb it.1/2 plant species Europe become extinct.

HURRICANES Hurricanes start tracking across the Atlantic striking in Europe. Cyclones devastate places as far removed as Texas and Shanghai.

Four Degrees

DROUGHT Further international decline in agricultural production due to drought, reduced river flows, lake disappearance and desertification.

MANKIND Collapse of civilisation.

HEAT 70% summer rain fails in Mediterranean, heatwaves last 65 days longer than presently, wildfires occur in the Alps. In the UK summer temperatures reach 45°.

PERMAFROST Permafrost in Siberia melts, releasing a 700% increase in carbon. Even just of 1% permafrost disappearance equals a doubling in present global emissions.

SEA LEVEL With sea levels rising further Mumbai, Shanghai, Boston, New York and London would be inundated to name but a few.

Five Degrees

DESERT New deserts in Sind, Indo-china, Korea, Japan and the west Pacific and Pacific Isles, Southern Europe, East Africa and Madagascar and parts of Chile.

MANKIND Humans will herd into shrinking habitable areas. Habitable areas will shrink towards the poles. Massive reduction in the supportable population. billions will die.

HEAT Inland temperatures 10° or more higher than now.

PERMAFROST Antarctica starts to melt. No ice sheets remain.

OCEAN Release of methane hydrates from the ocean floor due to changes in deep ocean temperatures.

Six Degrees

MANKIND We are in the realms of dystopia. The human species may survive a 6° temperature rise but it is by no means certain.

HURRICANES The volatility of the climate will see hurricanes throughout the planet of unimaginable ferocity.

SEA LEVEL Sea levels are 20 m higher than current. With Antarctica melting completely, sea levels eventually will be 73 metres higher. Go to map.

Want to know more about sea level rise? Read the article Sea Level Rise: What it is, Why It Matters, and What Can Be Done? by John Hawthorne


If we do act now

Currently, in 2014, CO2 levels in our atmosphere are just over 400 ppm. Now, this probably won’t mean a lot to you. Not even when you are told that the safe level of carbon dioxide in the atmosphere is 350 parts per million. This post attempts to give ‘ppm’ some context.

All this excess greenhouse gas will lead to actual warming. Not many people know that the warming effects are delayed. They think climate change is not true, because “It’s not really getting any warmer”.

This data visualization below takes you on the path of global implementation of the most optimistic ‘Act Now’ scenario: 

  • The ending of deforestation
  • A halving of emissions associated with food production
  • Global emissions peaking in 2020 and then falling by 3 per cent a year for a few decades.

If that path is taken we will pump out an extra 3000 Gt of greenhouse gas, making atmospheric concentrations of greenhouse gases rise to 650 ppm, associated with a global temperature rise of 4 to 6°C.

CO2 level in our atmosphere and global temperature rise due to climate change
CO2 level in our atmosphere and global temperature rise due to climate change

The delusional thing about global warming is that actual warming effects are delayed. What does that mean? Think about what happens when you put the heating on in your home. It takes a while for the temperature to rise. The same is happening right now in the atmosphere. Once the oceans and the atmosphere are fully heated up – like the radiators in your home – the temperature will go up. However, once it’s nice and warm, we can’t switch off the sun. Or get rid of the greenhouse gas that traps the heat from the sun. In fact, it will stay there for at least one millennium.

Words of support from Professor of Public Ethics Clive Hamilton:

‘If we do act now’ is a powerful visual representation of the threat posed by global warming and I fervently hope it will catalyse many people to accept that the Earth and its human population faces a very nasty future. That may be a despairing conclusion, but it is based on the best science available. We will not know how to respond properly until we have felt the despair a person experiences when they find the courage to face the truth of what the scientists have been trying to tell us.


1. The world’s most current data for atmospheric CO2 is measured at the Mauna Loa Observatoy in Hawaii.

2. Why 450ppm is dangerous and why 350ppm is safe

3. Kevin Anderson and Alice Bows, ‘Reframing the climate change challenge in light of post-2000 emission trends’, Philosophical Transactions of the Royal Society, Royal Society, 2008. Referred to in ‘Requiem For A Species’ by Clive Hamilton.