So firestorms suck up the N2O, push it up into the
stratosphere, and degrade the ozone layer. But where does this
stuff come from?
N2O is among a wide class of what we call tracers that are emitted
at the ground. It's produced by bacterias in soil, and it's been
increasing due to human activities like nitrogen fertilisers used
in farming. N2O is actually now the most significant human impact
on the ozone, now that we've mostly taken care of CFCs.
You did similar
computer simulations in the past few years and
saw this ozone-depleting effect. What
do the new simulations tell us?
Before, we couldn't look at the ozone depletion's effects on
surface temperatures; we lacked a full ocean model that would
respond realistically. The latest runs are ones I've done in the
Community Earth System Model. It has an atmospheric model, a
full-ocean model, full-land and sea-ice models, and even a glacier model.
We see significantly greater cooling than other studies, perhaps
because of ozone loss . Instead of a globally averaged
1.3-degree-Celsius drop, which Robock's atmospheric model produced, it's more
like 2 degrees. But we both see a 7 percent decrease in global
average precipitation in both models. And in our model we see a
much greater global average loss of ozone for many years, with even
larger losses everywhere outside of the tropics.
I also gave this to my colleague Julia
Lee-Taylor at NCAR. She calculated the UV indexes across the
planet, and a lot of major cities and farming areas would be
exposed to a UV index similar to the Himalayas, or the hole over
the Antarctic. We're starting to look at the response of sea ice
and land ice in the model, and it seems to be heavily increasing in
just a few years after the hypothetical war.
What would all of this do to the planet, to
UV has big impacts on whole ecosystems. Plant height reduction,
decreased shoot mass, reduction in foliage area. It can affect
genetic stability of plants, increase susceptibility to attacks by
insects and pathogens, and so on. It changes the whole competitive
balance of plants and nutrients, and it can affect processes from which
plants get their nitrogen.
Then there's marine life, which depends heavily on phytoplankton. Phytoplankton are essential; they live in top
layer of the ocean and they're the plants of the ocean. They can go
a little lower in the ocean if there's UV, but then they can't get
as much sunlight and produce as much energy. As soon as you cut off
plants in the ocean, the animals would die pretty quickly. You also
get damage to larval development and reproduction in fish, shrimp,
crabs and other animals. Amphibians are also very susceptible to
A 16 percent ozone depletion could result in a five percent loss
in phytoplankton, which could result in a seven percent loss in
fisheries and aquaculture. And in our model we see a much greater
global average loss of ozone for many years; the global average
hides a lot.