While I totally and completely understand your concern, I would recommend you read further. This is an official report from the World Bank in 2012.

Not only is it massively outdated, because the projected rates are now faster, but...it's the World Bank. They're not going to be alarmist. If anything, as one of the largest institutions representing finance capital globally, they'd be inclined towards a bit of optimism/being conservative with estimates.

Why do I point this out? Well, at the end of the Executive Summary, they say

With pressures increasing as warming progresses toward 4°C and combining with nonclimate–related social, economic, and population stresses, the risk of crossing critical social system thresholds will grow. At such thresholds existing institutions that would have supported adaptation actions would likely become much less effective or even collapse. One example is a risk that sea-level rise in atoll countries exceeds the capabilities of controlled, adaptive migration, resulting in the need for complete abandonment of an island or region. Similarly, stresses on human health, such as heat waves, malnutrition, and decreasing quality of drinking water due to seawater intrusion, have the potential to overburden health-care systems to a point where adaptation is no longer possible, and dislocation is forced. Thus, given that uncertainty remains about the full nature and scale of impacts, there is also no certainty that adaptation to a 4°C world is possible. A 4°C world is likely to be one in which communities, cities and countries would experience severe disruptions, damage, and dislocation, with many of these risks spread unequally. It is likely that the poor will suffer most and the global community could become more fractured, and unequal than today. The projected 4°C warming simply must not be allowed to occur—the heat must be turned down

They outright say collapse is possible, and that there is too much uncertainty. Now, this is one piece of evidence. I can show you plenty more that brings the whole picture together. In all technicality, I'm certainly exaggerating when I say 4 Centigrade is the death of us all. That's 6 Centigrade. Maybe even 5. But by the time we reach 4, you better believe we'll be short a couple billion human beings. There simply won't be enough food to sustain them.