Let’s suppose we see a 21st century full of natural disasters — like the 19th century:
How do we start out? Well, I’m going to ignore the Little Ice Age that spanned centuries and didn’t end until 1850 because obviously we aren’t already in a mini Ice Age. So lets start with the first big unique natural event of the 19th century.A geologically calamitous 21 century might start in December 2011 when along the Mississippi river in the center of the United States an earthquake equivalent to the December 16, 1811 New Madrid earthquake would begin a series 8.1 and 8.2 earthquakes over a period of a few months that would cause rivers to run backward, the Mississippi to change course (with far more calamitous results given much higher population densities) and church bells would again ring as far away as Boston. Picture bridges across the Mississippi collapsing with freight trains halted and river freight shipping blocked. A repeat of the New Madrid Missouri earthquakes would cause far more devastating damage than they when when that area was sparsely populated and the Mississippi was not used to move huge amounts of agricultural and other freight.
Of course, the most massive devastating earthquake of the 21st century might hit New York City or Tokyo or perhaps some other densely populated region (and the world has many more densely populated regions than it did in the 19th century). Even a repeat of the August 10, 1884 magnitude 5.5 quake near NYC would cause a lot of damage. A Big One will hit Los Angeles in the 21st century. The city of angels is overdue for The Big One. We are overdue for an earthquake that could go to near 8.0 similar to the 1857 SoCal quake which was about 7.9 on the Richter scale. But we’ll also witness earthquakes in places where they occur less often. Perhaps Shanghai? Hong Kong? Jakarta? Or how about New Zealand and with a volcanic eruption thrown in that requires lots of people to evacuate?
What next? A VEI (Volcanic Explosivity Index) 7 volcano. Likely location: Indonesia. Now the 4th most populated country in the world. On April 10th 1815 Mount Tambora erupted with VEI 7 intensity.. The eruption so reduced solar radiation reaching the surface that snow fell in New England and the Canadian Maritime provinces in June. You can imagine what that did to crop yields. People went hungry, causing the biggest famine of the 19th century. And get this: 1816 had even worse cold weather and bigger crop failures. So imagine 2015 and 2016 with worldwide crop failures in a world with 7 billion people, all due to a very plausible VEI 7 volcanic eruption.
What would 2016 be like? Food prices would be very high, too high for the poorest to afford. We’d see civil unrest and rioting in many nations. Revolutions would be likely. The cold weather would increase demand for heating oil, natural gas, coal, and wood for heating. So energy commodity prices would soar along with agricultural commodities. Many countries (possibly including the United States) would ban the export of grains.
No doubt 1815 and 1816 were difficult years for many other mammalian species as well. But a VEI 7 eruption in the early 21st century would cause much bigger problems for orangutans, gorillas, big cats, and other threatened species for a couple of reasons. First off, their numbers have already fallen in the last couple of centuries by orders of magnitude. So they already are living close to the edge of extinction. Pretty small disruptions to their food supply run much greater risks of wiping them out. Second, with much larger numbers of humans living near them now they face much greater risk of being hunted to extinction by hungry humans.
So at least one big earthquake and a pretty big volcano with two lost growing seasons. The century is still young. What’s next? On September 2, 1859 an unusually large coronal mass ejection by the Sun cause intense magnetic fields on Earth which if they happened today would cause a large fraction of the big electric power transformers to fail in large electric grids. Large areas of industrialized countries would be without electric power for months. Picture cities evacuated due to lack of power to operate water pumps. Picture massive computer server farms sitting dark. Banks would fail.
The 19th century also featured a VEI 6 volcano, the well known Krakatoa eruption in 1883. This wasn’t as severe as the 1815 eruption. But it would cause a global cooling and crop losses.
The 20th century was a relatively mild, wet, and calm century as compared to the 19th century. We would make a mistake to expect the 21st century will be as calm as the 20th. The current low level of sun spot activity could continue and we could go thru a cooler period in spite of our CO2 emissions. Or we could have severe cooling periods caused by large volcanic eruptions. Also, earthquakes could hit major cities or cause tsunami damage. Do not be shocked if a severe turn of events happens. Even the early 20th century had a dramatic event in 1908 with the Tunguska asteroid explosion over a large swath of Siberia.