Four Degrees

In this chapter of Six Degrees, Mark Lynas talks about what our world will look like under four degrees of warming. There are many different topics discussed in this chapter including rising sea levels from melting glaciers which will effect people living on the coast, droughts and heatwaves resulting in decreased crop production and extra carbon being released into the air from melting permafrost draining into rivers and lakes.


I think that the five main points of this chapter are the following.

1. The Antarctic and Arctic ice caps and glaciers are melting. The more the ice starts to melt on the edges the faster it will completely melt all the way to the center. As the ice melts it raises the sea level which makes it more and more likely for cities in coastal regions to be under water. Once the sea level rises past a certain level it is almost always guaranteed to stay that way. There is no going back, at least until another ice age comes along.

2. Increased drought almost world wide. There will be many climate changes around the world, but the one with the most impact is droughts. For example, southern Europe will become more like the desert-like climate of northern Africa or the Middle East. The decreased rainfall and snowfall in winter, means even drier summers, getting more extreme as the years go on. Adding to this the extreme heatwaves coming to the world, gives the impression of a major climate change for Europe.

3. A huge impact comes from "worldwide agricultural drought" as Lynas puts it. As climate change impacts the world population growth is becoming a problem that is growing to almost the same point. With more people in the world and more countries becoming developed the world needs to be able to provide more food. However, with the droughts and soil loss there is less and less areas for farmland. One of the things Lynas said that stuck with me was "if every Chinese were to live like an American, it would double the human environmental impact on the planet" (pg.194).

The countries that are mostly impacted by the drought are also the countries that produce most of the world's food

4. Erosion of soil from rain. In a world with four degrees of warming, there will be change in rainfall (a general decrease), and the rain that does fall, will come down hard and fast, not giving the ground time to absorb it. The rainfall that comes brings large storms along with it. Even in places where the soil is still fit for growing crops after the heatwaves have come through, they will not last long because the increased ferocious rainfall will wash out the good soil and leave desert-like soil behind.

5. Melting permafrost in the northern half of the world will cause a major increase in carbon being put into the atmosphere. As the temperatures rise in northern countries the areas that are normally frozen year round are melting. These areas of permafrost are holding areas of carbon in them. As they melt the run-off created contains large quantities of CO2 that is then carried to from rivers into lakes and oceans. This creates a type of positive feedback loop where the CO2 put back into the atmosphere creates another rise in temperature, which results in more melting and more CO2 in the run-off.

Lynas ends the chapter by talking about this feedback loop and how if the world makes it to three degrees of warming it will lead to four, and eventually to five, and so on. He seems to think if the world makes it past three degrees of warming, then the world really doesn't have much hope.