I think that's what Endymion says is the reason for the "great freeze," but something that looks like meteorites are displayed as "ecological disaster" is being said, but wouldn't that be a natural disaster instead?
He could be talking about the effect. Ie, the cause may be a natural disaster, but the effect is an ecological disaster.
Actually, is there anything considered to be an ecological disaster that could lead to the whole world freezing over?
Just by itself? Yes. But AFAIK, unlikely to happen. For example, there are microbes that "eats" CO2 and other greenhouse gasses, if for some reason there was suddenly a new type of such(or a growth explosion of them for some reason) and they went om-nom-nom you could get a serious cooling effect.
If you get too much plants that converts CO2 into oxygen while binding the carbon, you could end up with massive firestorms because of high levels of oxygen in the atmosphere. (this is why(or one reason at least) smoking is NOT permitted in hospitals, because there´s use of pure oxygen, and if that is ignited it can even explode)
In fact, there´s probably thousands of things that are theoretically possible.
For example, take a look at this:
http://en.wikipedia.org/wiki/DaisyworldDaisyworld examines the energy budget of a planet populated by two different types of plants, black daisies and white daisies. The colour of the daisies influences the albedo of the planet such that black daisies absorb light and warm the planet, while white daisies reflect light and cool the planet. Competition between the daisies (based on temperature-effects on growth rates) leads to a balance of populations that tends to favour a planetary temperature close to the optimum for daisy growth.It´s a very interesting article regardless.