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Climate
and Hydrologic Research
Interview with Chris Milly
July 18, 2007
BARRY
REICHENBAUGH: This is Barry Reichenbaugh with the NOAA Research Communications
Office. I'm with Chris Milly of USGS here at the Princeton, New Jersey,
Geophysical Fluid Dynamics Laboratory. Chris, welcome.
I'm wondering
if you could start us off here by explaining just what is a US Geological
Survey employee doing here at GFDL?
CHRIS MILLY: Well, sure. GFDL is a NOAA
lab and NOAA is responsible for looking at oceans and atmospheres. One
of the things GFDL does is try to understand climate, and the climate
system includes the oceans and the atmospheres but also the land. Land
is where all the water is that we use and land is coupled to the oceans
and the atmospheres.
So, although oceanographers and atmospheric scientists
have a fair understanding of how the land interact with them, they felt
it would be useful to have a little more expertise from the land side,
from a hydrologist, someone who studies water on the land. And, that's
why some 20 years ago, the USGS and NOAA GFDL got together and said that
they thought there should be some researchers working together on this
problem.
BARRY REICHENBAUGH: Could you maybe offer an example
to clarify just what you mean by the human interaction piece of this?
CHRIS MILLY: Yeah, of course. Much of
how we as humans experience a climate system is coming through the fact
that water is part of the climate system. We, of course, our bodies are
mostly water. We keep our bodies hydrated by drinking water. We keep
our bodies clean by washing in water. We nourish ourselves by eating
food that's been produced with one of the main inputs being water. We
have developed societies. We have manufactured products whose manufacture
relies on processing using water and relies on energy whose production
in turn consumes large amounts of water.
In fact, we use water directly
in hydroelectric plants to generate electricity. We transport our products
through the rivers, over water. The fish and fowl that we enjoy in nature
rely in turn on water.
So, these are the things that make the connection,
really, between the climate system and human society.
BARRY REICHENBAUGH: Okay. Here is where I think
I want to ask about water availability. Or, do you think we've covered
that?
CHRIS MILLY: Yeah -- so -- I mean, we
talk about how, you know, how -- I mean, when I talk about water, that's
kind of a vague thing. I mean, what specifically? There's precipitation,
there's stream flow, there's soil moisture, there's groundwater, there
are glaciers, there are lakes. And so, it's a multidimensional kind of
thing. How do we, you know, when we do science, we want measurements
so that we can be quantitative and we can relate our models and our theories
to the real world and we can test models and theories and so forth.
Well,
the measurement that a lot of us hydrologists use is that of stream flow.
How much water is flowing past a given point on a river or a stream as
a function of time? This is a measurement that can be made very well,
has been made for many decades over many river basins in the world. It's
a quantity that integrates over large areas upstream of the point where
one is measuring.
So, we can get an idea what's going on in the heartland
of the US simply by monitoring the flow of the Mississippi at Vicksburg
over time.
This is something that then allows us to sort of link in
observations to the modeling activities such as those going on here at
GFDL. GFDL models produce runoff from the land. We route it. We construct
models of the water system as part of the GFDL climate modeling efforts.
And, as part of that, we route the runoff from climate models down the
rivers and we generate synthetic stream flows of the Mississippi at Vicksburg
and we can compare those to the actual observed stream flows.
So, a lot
of the work we do is in trying to look at how realistic the climate models
are with respect to water. And, relate climate model projections to projections
of water availability. And so, the stream flow, again, it plays a really
important role there because it is a very direct measure of water availability.
And, much of our water use comes out of flowing rivers.
BARRY REICHENBAUGH: Can you tell me a little bit
about how you're using the GFDL climate model in the research you're
involved with?
CHRIS MILLY: Of course. GFDL scientists
who model the global climate system which -- and, part of the global
climate system is the global water cycle. So, we can look at what's going
on in the climate models here and relate that to what's going on that
we know of from real-world observations and see how they agree, see where
they disagree, where there's room to improve on the model, and where
the model can give us some idea about what's going to happen in the future.
We conducted a study where we looked at the GFDL model's
ability to say how stream flow ought to have changed during the course
of the 20th century. We compared that to observations of stream flow
trends around the world and showed a degree of correspondence that is
actually much too high to be explained as a natural coincidence but rather
indicates skill of the GFDL climate model.
And, we built on that to look
forward in the future and say, well, the model seems to have some credibility
based on its track record. What does it say about the future of stream
flow runoff, water availability?
BARRY REICHENBAUGH: Can you get a
little bit into the results of what you're finding, the projections?
CHRIS MILLY: Yeah. The projections for
changes in water availability going into the current century, say by
the middle of the 21st century, are, of course, like many other things
with climate projections, highly uncertain. However, there are some areas
of strong agreement among various models including the GFDL model on
which areas of the world may be expected to be coming wetter or drier
with respect to say amount of stream flow expected in a year.
There are
some areas where the models project that less rainfall will be falling,
more evaporation will be occurring and, as a result, the bottom line,
the stream flow, the runoff, will be reduced.
These are areas like southwestern
North America, the Colorado River Basin, for example. In Europe and Africa,
the Mediterranean region that would be northern Africa, the Middle East,
and southern Europe -- all projected to have a sustained period of drying
during the 21st century.
Southern Africa is another such region where
the majority of models agree on a rather robust signal of drying. There
are also regions that are expected to receive more water, generally these
are regions where there's no shortage of water historically in the first
place; regions like northern North America, that's Canada, Alaska, Siberia,
all of northern Eurasia, and some tropical regions.
BARRY REICHENBAUGH: Okay. Let's shift over to a different
but related topic. And, I'm wondering if you could just talk a little
bit about how you became a scientist, what got you interested in science?
CHRIS MILLY: Yeah. How did I become a
scientist? I got interested in things quantitative in my early years
in school simply because it was interesting. Math and science courses
were interesting. I was a child of, sort of, the 60s and 70s so there
was, sort of, a natural interest in the environment.
And, when I went
to college, I just sought those areas where I could kind of merge this
sort of aptitude and interest in math with the kind of interest in natural
sciences, Earth sciences, environmental sciences.
And, I ended up in
civil engineering, which is where hydrology traditionally has been taught
and studied. Hydrology, even though it's one of the Earth science, because
it is such a practical one, has ended up being taught and studied by
engineering rather than science faculty.
So, I went into civil engineering.
I got a couple of degrees in civil engineering, studying water. And then,
I went into research and I somehow, just the luck of nature, I stumbled
into the US Geological Survey, which is a wonderful place to do research.
And then, the second big stroke of luck was getting into
this sort of collaboration with GFDL. I'm really kind of going off from
your question here. It's a good question.
BARRY REICHENBAUGH: You were just anticipating my
follow up question.
CHRIS MILLY: Yeah.
BARRY REICHENBAUGH: I guess I'd
like to end with just, you know, your thoughts on what you say to someone
who is interested in pursuing a career in science.
CHRIS MILLY: I would say to one who is
interested in pursuing science to go for it. It's an area where our country
has a very surprisingly small number of students entering the field.
And, if the student feels some interest in it, it's a real opportunity
because it's under stocked field -- what is it? It's an understaffed
field. It's a wonderful life doing research if you enjoy it. And, I think
it's a very useful sort of profession that they can return a lot to people
in its benefits.
BARRY REICHENBAUGH: Chris,
thanks for joining us.
CHRIS MILLY: Okay, Barry. Thanks very much.