In my previous posts, I established, as is accepted in the scientific community, that global warming is a real phenomenon, and that human activity is what drives this warming trend. However, as alarming as the data appears, it makes sense to question what this actually means. What does a warming world look like? Would it truly have a negative effect, and if so, how severe would it be?

The last question is the subject of the World Bank’s 2012 report on climate change. Titled “Turn Down the Heat: Why a 4 °C Warmer World Must be Avoided,” the report claims that our present course is towards an Earth whose average temperature is a full 4 °C higher than today. Of course, to Americans, 4 °C doesn’t sound like a huge jump. But 4 °C amounts to a 7.2 degree increase on the Fahrenheit scale. If we were talking about warming a home, a change of 7.2 degrees can be the difference between just a bit too chilly and slightly too warm. Moreover, this isn’t a flat change: this is a change in the Earth’s averagetemperature, which means we can expect not only to see warmer days, but changes in both local and global patterns of weather and climate.

So, what do we expect the effects to be? Devastating, in a word, and to some more than their equal share. The melting of polar ice would raise sea level by an average of .5 to 1 meters (about 20 to 40 inches), according to the World Bank report. Coastlines around the world would retreat, flooding coastal cities and island nations alike. The more modest sea level rises expected from a 1.5 °C increase are already considered dangerous to coastal and island economies. The rise in sea levels caused by a 4 °C increase would be far worse, and in some cases could sink them. Likewise, the report notes that we can expect the recent trend of frequent, intense hurricanes (like Sandy) to continue and intensify as the world heats up.

Of course, we could run inland. But the climate there isn’t much nicer. The World Bank projects a far drier climate for much of the world, including the south of Europe and Australia, much of North and South America, and most of Africa. (The report notes that some areas, typically the parts of the Americas and Eurasia that are furthest north, will actually be wetter, but the trend seems to be towards dryness.)These more arid climates would have less arable land, reducing the supply of food. Combined with present trends of population growth, hunger and scarcity would increase drastically. The fact that intense heat waves, the likes of which seen in the summer of 2010 in the northern hemisphere, would be a regular event only worsens the situation. With more frequent and intense heat waves comes more frequent and intense drought, wildfires and other disasters. These also would shrink the already anemic food supply. Winter wouldn’t be a good time to cool off from this heat, either. “In this new high-temperature climate regime,” says the report, “the coolest months are likely to be substantially warmer than the warmest months at the end of the 20th century.”

The literature on climate change, and the World Bank report itself, presents a litany of devastating effects on human, animal, and plant life that would force civilization into a time of intense hardship. Depending upon how long warming continues, that hardship will intensify. What is most striking about the World Bank report, however, is how so many of these negative effects exacerbate the problems we know today. For example, the 4 °C warmer world does not affect all regions—or countries—equally. Equatorial, coastal and island regions seem to be hit the worst, as well as smaller and developing countries. The report anticipates that those experiencing hardship, as well as those who are forced to abandon their homes to flood and drought, will strike out in search of less yellowed pastures. By and large, we may expect them to gravitate towards the wealthier nations, where land and resources are more plentiful. Our present debates on illegal immigration in the United States would be nothing compared to the immigration matters facing us in 2100. The 4 °C world is our world—we will still have the same problems. They will, however, be far, far worse.

The World Bank’s projection of a 4 °C average temperature increase by the year 2100 includes both present and proposed strategies to reduce greenhouse gas emissions. Even if every country in the world fulfills its promises, it will not be enough to stop such a disaster.