Climate Change

Solar insolation is a measure of how much of the sun’s energy hits the Earth’s surface. This energy drives the climate and weather of our planet. The seasons are caused by the planet’s tilt— half of the planet gets more direct solar radiation in Summer than in Winter.
However, solar insolation itself can vary on timescales from tens to hundreds of thousands of years, as a result of changes in the planet’s tilt, the wobble on its axis, and the shape of its orbit. Carbon Dioxide (CO2) and other atmospheric gases vary in time because complex interactions among processes in the oceans, atmosphere and biosphere (life) affect the amounts of these gases that are stored in the air, ocean, and on land. Here is a movie of the variations of solar insolation and CO2 over the last 800 thousand years:

As you can see and hear, something ridiculous happens right there at the end. Humans figured out how to extract carbon from the Earth’s crust in various forms and burn it for heat and power, and rapidly expanded our societies around it. In a geologic instant, we have put far more CO2 in our atmosphere than has ever existed over the past 800,000 years.

[include plot of various sources of human emissions of CO2.]

Now we zoom in to the last 60 years:

Zooming in on the last 60 years shows the scale of human carbon emissions, and the correlation between the levels of CO2 in the atmosphere and the yearly average global temperatures. The difference between human emissions and atmospheric CO2 reflects how much carbon the oceans and biosphere can absorb, or buffer. We have diminished the capacity of the oceans and plants to absorb carbon in CO2, methane and other gases, increasing the strength of the greenhouse effect.

Feedbacks will emerge and cause changes in the climate system, leading to rising global temperatures and more frequent and intense extreme weather events. While our best climate models incorporate an incredible level of complexity, we cannot fully predict what these changes will be, as the ocean/atmosphere/biosphere is still more complex than our computer models.

Hurricanes are on the edge of that interface between weather and climate. Here is Owen Evans’ movie, made in collaboration with Chia-ying Lee at LDEO:

2005 and 2017 had extremely large numbers of powerful hurricanes. In 2017, there was a storm so large that it blew past the highest category of 5. It broke apart into about 3 different very large hurricanes, Maria, Hugo and Irma. Because the movie is made from the category scale, our movie doesn’t really show how large that storm system was, but as the climate warms, these kinds of things are likely to happen more often.

[put in a graph showing number and intensity of hurricanes in the last 20 years, and some predictions.]