Much ink has been spilled over all the potential dangers of global warming (or as has been recently rebranded--climate change). Hurricanes, rising sea levels, encroaching deserts--things these things have been happening to the planet since the end of the last ice age--are predicted to get progressively worse due to the warming of the planet. On the other hand, there are benefits to a warming planet. These include longer growing seasons, a net increase in habitable areas of the planet, and higher biodiversity. How do we know this? From both the fossil record and historical record from warm ages.
For instance, the first known explosion of biodiversity, the Cambrian explosion, happened only after the greatest ice age the planet has ever experienced had ended, also known as "Snowball Earth". Typically, other time periods where the Earth was warmer, also resulted in increased flora and fauna. For example, in the Early Carboniferous, which was warmer than today, plant growth was extensive and thick (due to higher CO2 and higher temperatures) and bacteria that break down plant matter did not yet exist; it resulted in the coal seams we have today. There is also the Mesozoic Era--the time of the dinosaurs--which was far warmer than it is today and there was a great diversity of animals. The first mammals and birds developed alongside the dinosaurs during this time. Even during one the most massive global warming events scientists have on record, also known as the Paleocene-Eocene Thermal Maximum 56 million years ago, terrestrial animals thrived even though marine species died out. In fact, this was the time when our ancestors, primates, first appeared on the scene.
There are also human recorded events of times warmer than today. During the Medieval Warm Period, temperatures were so warm in the Northern Hemisphere, that wine grapes were grown in England. Greenland was warm enough to support a sedentary population, and Vikings even led excursions into North America long before Columbus. The High Middle Ages were in fact a time of relative plenty and cultural development. Our stereotype of the "Dark Ages" comes from the prejudice of the generations following the end of the warming period which resulted in famine, and the Black Plague probably didn't generate warm fuzzy feelings either. While the West eventually recovered, life during the little ice age was no picnic. Sure there were scientific and cultural advancements, but life for the common man really didn't improve that much over the medieval era. The shorter growing seasons resulted in crop failures, even to the point of having a devastating year without a summer.
One counterpoint I will address is what happens if the worst climate predictions of the next 100 years are true? Will any benefits be outweighed by the negative consequences? I'm convinced that even the worst warming will open up more land to human utility than is lost, as during warming periods tend to warm up the poles to a greater degree than the equator. Compare the vast frozen interiors of Siberia, Canada (and possibly Greenland and Antarctica) that will become warmer and more habitable, to arid areas near the equator that face desertification. Of course there will also be land lost due to rising sea levels, but even the greatest modeled sea level rise between 1990 and 2100 would be only 770 millimeters. Compare this to the late stone age when sea levels were three meters higher! The sea level change will be so gradual that any affected populations could easily move out of the way, probably a cost much cheaper than climate mitigation (can we just call it terraforming?), but that will be the topic of my proceeding post.