Okay, so now we're going to talk about how we can address climate change by looking at the sinks of greenhouse gases,
and also how changes in society can have secondary benefits to climate change. As we think about these issues, one of
the best places to begin is supporting nature's carbon
cycle. These are things that are naturally sinks of
greenhouse gases today. If we zoom in here, we can see how
forests and oceans are absorbing over 40% of the pollution
we put in the atmosphere every year,
most of that in the form of CO2.
And so if we can support those sinks and make sure they stay healthy,
that would help us address climate change into the future. But the problem is, some of these
systems aren't that healthy right now. A lot of our forests are feeling the weight of climate change already or being
torn down. And our oceans are getting warmer and more acidic and they're also getting more polluted and over-harvested
at the same time. So job number one here is just
kind of support nature, give it some backup,
and make sure that it isn't diminishing the sinks we already have. Later, hopefully, we can augment those sinks by putting
other land and other ocean systems into production and add to what nature is doing already.
But here's the math we've got to start with: 100% of these emissions are coming from us.
Land is putting out about 24% or
removing it and putting it into our forests.
The oceans are pulling out about 17% of the greenhouse gases
and putting it into different parts of the ocean.
Interestingly, even though oceans cover a lot more of the Earth's surface, they actually take up less of the
carbon than the land does. Oceans are important, but forests are kind of a big story here. Altogether, that still leaves
about 59% of the greenhouse gases in the atmosphere. And so this is part of the solution, but it can't be the whole
solution. And before we look at the individual sinks, there are about four major points I think we have to talk about
before we even get started. First of all, it is crucial that we give nature support because nature is already doing 40%
of all the removal, and we're doing zip. So starting with backing up nature, giving it support, and making sure we
don't lose that service of removing greenhouse gases is crucial. Then once we kind of get that stuff secured, we can
also maybe add some of our own new carbon sinks by planting new trees or farming new areas in different ways, or maybe
machines that pull carbon out of the atmosphere, all of that. But first, why don't we help out in nature that's
doing a good job already.
The second thing to remember is sinks all have limits. They can't take an infinite amount of greenhouse gas out of the
atmosphere. There's no way. Trees only get so big. Soils only go so deep and can have so much carbon in them. Coral
reefs can only grow so fast. So we have things that have a limited capacity to absorb our greenhouse gases. That's why
it's probably more important to stop them before they ever get in the atmosphere than try to remove them later. And
that leads to a third point. Sinks take time to absorb greenhouse gases. If you put out a tonne of CO2 today and
plant trees to offset that, it might take a hundred years for those trees to grow fully to maturity, absorbing carbon out of
the atmosphere. But in the meantime, you've got a hundred years of climate change caused by the pollution you started with. So
you can't really get away with this by planting trees to offset emissions, introduces a time lag where climate change
is just going to be worse. There's kind of an asymmetry here. Turning off a power plant stops pollution today.
Planting trees or building coral reefs or whatever, basically is a solution for 50 to a hundred years from now.
The other thing we have to worry about is sinks may not always be permanent. They might not be secure. For example, some of
our sinks are biological in nature: growing a new tree, putting stuff in the soil, putting stuff in a kelp forest, or
whatever. Those are biological sinks, and they're great. But they can also be reversed. We can plant trees, and then they
could be burned down. We could farm really well and build up the soil, but that farmer retires, the next one comes in and
plows it all up, and it goes back in the atmosphere instantly. So these kind of biological sinks can sometimes
be quite ephemeral. They may not be permanent. But some sinks might be more geological in nature. If we can lock up
carbon in kind of like a rock or something like a coral reef or down in the basalt or something like that, then we've got
something that's locked up pretty much permanently, at least on human timescales.
So let's look at these sinks one by one. On land, again,
it takes up about a quarter of our emissions, which is
pretty amazing. And it's doing it with photosynthesis.
The natural vegetation of our planet, especially trees,
are growing a little bit faster now,
and they're accumulating more biomass, or essentially wood. And when those things die, they build up a little more carbon in
the soil, what we call soil organic matter.
So photosynthesis, biomass of the living stuff, and soil
organic matter. That's where all the carbon goes. And we can
help maintain those sinks in nature by leaving nature
alone. We can first take pressure off of nature by not
clearing forests, for example. And that's where food waste,
and diets, and things like that, where we don't need to grow more food and invade those forests because we're more
efficient with the food we already grow. That’ll be crucial.
But also putting up kind of big protections around the
remaining rainforest and peatland forest and other
ecosystems, to make sure they're never cleared at all.
And then, once we've kind of taken care of nature and secured it,
then we can do exciting things like putting our farmland
into new types of agriculture that might absorb carbon, what
we often call “regenerative agriculture.” So we looked at
these solutions. We looked at food waste and diets, not by just reducing emissions, but preserving sinks. We looked at how
protecting forests didn't just reduce the deforestation emissions, it kept the forest sinks intact, too.
And then we looked at how changing agriculture and degrading lands back into production and reversing that can be really
important as well. One of the things I want to mention though, is regenerative agriculture is getting a lot of
attention these days. This idea that farms and ranches could be farmed differently to absorb carbon. That is true.
There's a lot of great evidence showing that we can grow crops and livestock in ways that can actually absorb carbon,
whether in trees in the forested areas around the farmland, or in agroforestry, or in the soil itself. And
that's really exciting. But there are limits to how much this can happen. There's only so much soil they can build up.
There are only so many trees you can build up, and they are all kind of temporary. The next farmer or a drought or a
fire could disturb all of them, putting them back in the atmosphere. So be careful there. There's also a few groups
that are not really paying attention to the science, I would say, that are making big bold claims that regenerative
agriculture can absorb all of our greenhouse-gas pollution. That is just not true at all. The scientific community is
quite clear that it is a solution. But it's one of many solutions, so we've got to make sure we balance it with all
the others. So when we look at the numbers, we see that protecting ecosystems and reducing food waste kind of
protecting and taking the pressure off of ecosystems, is critical here to preserving sinks. And then we can put the
farmlands and the degraded lands into better systems of agriculture so they absorb carbon too. So this combination
of kind of taking pressure off of land, protecting it, and then farming our working lands in different ways can be powerful
ways to maintain and enhance land-based carbon sinks. The oceans are kind of different. We don't manage the oceans as
much as we might on land. A lot of it's out in the open ocean where we don't do so much. Coastal oceans are another
matter, though. But either way, oceans as a whole, even though they take 71% of the planet, absorb 17% of our
greenhouse gas emissions. And they do it through three major mechanisms. One is what we call a “solubility pump.” That's
just a fancy way of saying CO2 dissolves in water. And what's interesting here is that salt water dissolves CO2,
just like fresh water does. But as water warms up, it absorbs a little less CO2 than cold water. So as the climate
changes, we can't really expect the solubility pump to get bigger. It's probably going to stay where it is or maybe
go down a little. Then we have something called the “carbonate pump,” which is where living animals pull carbon
dioxide and calcium out of the seawater, and they use it to build a shell or shellfish. Things like oysters and clams
and mussels, but also crabs and lobsters. They pull that stuff out of the water and build shells that stay there for
quite a long time. Corals are the same thing, too. Remember, corals are animals. They're not plants. They're not rocks.
They are little polyp animals that build a calcium carbonate shell around them that we call a coral reef. And
that takes CO2 out of the water as well. And then we finally have the biological pump which is just basically the plants
in the ocean. The little tiny microscopic phytoplankton and diatoms that do photosynthesis, as well as what we call
“macrophytes,” or big plants, like kelp forests. They do photosynthesis. They build bigger plants and those plants
will later die and get buried in the ocean sediment. So all of those things, whether it's just chemistry, building
shells, or growing plants, pull carbon out of the air, through the water, and tuck it away. We can do a little bit to help
already, obviously. For example, protecting the coastal
ecosystems from being developed or torn apart. Like
mangroves and wetlands and marshes
are critical carbon sinks. But also, they're turning out to be really helpful in
protecting our storm surges on the coastline. When we have healthy mangroves and coral reefs and marshlands and wetlands
along the coast, we don't have as much flooding or as much damage from storms. So it kind of helps us prevent climate change
but also adapt the climate change that is already here.
That's a good win-win in my book. But we might also be
able to add new carbon sinks out in the ocean, maybe through
farming kelp in big regenerative aquaculture systems. Or
maybe planting new coral reefs in oyster beds and lots of other things. We're just beginning to explore the
possibilities here, and I think they're going to be really cool.
So we looked at land and oceans, but then we can look to
machines to maybe become carbon sinks. There are machines out there, kind of in laboratory settings, and a few very
small pilots. The atmosphere is not noticing these things at all yet. They're way too small.
But the idea here is maybe we could build machines
that would pull carbon out of the atmosphere and either store it down in the rock somewhere or
tuck it away and lock it up or use it for something. That's the one that gets me really excited. If we could pull
carbon out of the atmosphere as carbon dioxide or whatever and use it to make plastics or jet fuel or other things
society might want without using oil at all! Use pollution to make our stuff, not new oil. Leave the oil in the ground.
We'll take the old stuff out of the air. That would be really cool. This is nowhere near being deployable right
now, but some of these technologies are very interesting. And over the next 10 years or so I think we're going to see a
lot more rapid development of these technologies, and they may start to play an important role. So we've looked at the
carbon sinks and before that the carbon sources. And we can see by reducing pollution, working with nature, and maybe
augmenting nature, we've got a lot we can do about climate change. But there's a third principle too, that improving
society, not because of climate change, but because it's the right and moral thing to do, turns out to be a great set of
climate solutions. It's kind of interesting. And it turns out
improving equality and equity, especially with women and
girls, for example. Improving the access to education and
health care helps women and girls see new opportunities
around the world. And as a consequence, women and girls will have maybe fewer children but healthier children, a little
bit later in life, than they might have otherwise had. And when that's the case, the growth of population in the future
might bend down earlier than we thought before. While population growth actually isn't really responsible for most
of climate change – most of the emissions are from rich people, not poor people – future population growth slowing
down will actually help us a little bit in the long run as population growth and economic development drive up
emissions in the future. So this is a great win-win by helping women have new opportunities,
we might actually help the environment and the climate as well.
So it turns out that helping people for lots of good reasons
actually can help us with climate change as well.
And this represents kind of a win-win
opportunity to improve human well-being,
as well as improving our future climate solutions.