I'll see if I can find the article, but I seem to remember several sources, including, if I remember correctly, one of the books on the Columbian Exchange, either
1492 or
1493, suggesting that the Virgin Field Epidemics that resulted from European contact in 1492 caused such severe disruption in plains management systems in North America that they succeeded to closed-canopy forests in the century following contact, causing massive CO2 draw-down and a resultant drop in global temperatures.
There are actually seven suggested causes, starting back in the 1300s, including orbital variations, solar and volcanic activity, effects on ocean circulation, increases and/or decreases in human population and activities, along with the inherent variability of climate. Wikipedia has a pretty good summary:
Little Ice Age.
I know we can look at all this, be fatalistic, and decide that there's nothing in it to inform our life choices. And on the personal level, you might be right, unless you're personally in a position to assist in the planting of hundreds or thousands of trees, and encourage others to do the same, and to nurture them as far along as possible. But I like to think that there will be people to plant those trees, and to encourage protected seagrass ecosystems, and rehabilitate and spread mangrove swamps. And yes, help the transition of the permafrost, which is happening whether we like it or not, into a diverse and stable ecological form that perhaps still traps the bulk of its methane and sequesters carbon. And yes, the likely transition of boreal forest to something more like boreal/temperate hardwood transitional forest ecosystems, where applicable, so that however the climate swings, we have species in place that will thrive.
So if we're in the middle of the next ice age, I just hope we can fix things to pre-industrial levels before it starts to warm up again, or I think we'll really be in trouble. We've been in a heat warning for over a week now, with nighttime temperatures not falling below 20 C and daytime temps exceeding 30 C, and feeling at times like 40 C+ with the humidity. And I live in Toronto. And I wish I could say that this year is an anomaly, but we know it isn't, nor is this decade.
-CK
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein