A new study shows that a global temperature increase of more than 1.5
degrees celsius will mean that dry air will increase significantly,
which can intensify desertification and crop failures. We speak with
Prof. Manoj Joshi, one of the study's authors
biography
Manoj Joshiis a senior lecturer in climate dynamics in the school of environmental sciences at the University of East Anglia, Norwich, UK. His area is climate science, climate models - and occasionally understanding climates of other planets.transcript
]GREGORY WILPERT: Welcome to The Real News Network. I'm Gregory Wilpert coming to you from Quito, Ecuador.
24 to 32 percent of the world will become arid deserts if we fail to
curb runaway human-caused climate change, according to a recent study.
The study, "Keeping global warming within 1.5 degrees Celsius constrains
emergence of aridification," was published in the peer-reviewed science
magazine Nature. Who would be most affected? And is this potentially
devastating scenario preventable? With us to discuss the study is
one of its authors. Joining us from Norwich, England is Dr. Manoj
Joshi, who is a professor in climate dynamics at the University of East
Anglia. Welcome to The Real News, Professor Joshi.MANOJ JOSHI: Thank you.GREGORY
WILPERT: The study consisted of projections of 27 global climate
models. What were the biggest takeaways from your study?MANOJ
JOSHI: The biggest takeaways, the main thing to point out is that we
focused on how certain regions of the world might encounter
aridification, or get drier, compared to the year-to-year variability of
the 20th century. We didn't say that these regions would become desert.
It's a very clear thing we have to say. We were saying that these
regions would simply get drier compared to the year-to-year variability
or variations that they presently get, which could have some significant
impacts in terms of, for instance, potential droughts or water supply,
forest fires, things like that.GREGORY WILPERT: A lot of the
media said that your study found that 25 percent of the world could
become arid deserts, so, I guess, perhaps distorting a bit of what you
were saying. But I understand there were also scenarios you modeled that
were as high as 32 percent, referring that is to increased
aridification. Was that the case, and what accounts for this
variability?MANOJ JOSHI: The reason we get, we say between 10 and
20 percent, these numbers tend to come in the variation of response in
climate models. Different climate models warm up by slightly different
amounts to a given level of carbon dioxide increase. It's something
called the transient climate response. This uncertainty is part of
trying to put together the sort of the climate projection jigsaw, as it
were. It's an uncertainty that policymakers, scientists know all about,
and it's unfortunately one of the things we have to deal with when
trying to make projections of the 21st century in terms of climate.GREGORY WILPERT: What is the difference in terms of aridity between a 1.5 and 2 percent warming scenario?MANOJ
JOSHI: The difference between, well, 1.5 degree and 2 degree warming
scenario is that slightly more regions of the world will encounter what
we call the significant or substantial aridification compared to present
day or late 20th century values. So the more you can restrain global
warming, the greater fraction of these areas can be prevented from
reaching this new significant aridification.GREGORY WILPERT: What
parts of the world would be most affected? Are we already seeing the
effects of climate change in terms of usable agricultural land?MANOJ
JOSHI: The areas we looked at mostly were the Central America and sort
of North and South America, the Mediterranean, Southeast China, and
Southern Africa. We are starting to see differences in circulation
patterns, obviously temperature. But it's important to note that when we
look at individual events or individual drought events, we can't say,
"Was climate change responsible for this individual event?" The question
is likelihoods. What climate scientists tend to ask is how likely was
such an event without human interference in the climate system,
emissions of greenhouse gases? And how likely is it now? How likely may
it become in the future? Those are the sorts of questions we are trying
to understand.GREGORY WILPERT: How do we know that this
desertification is due to human-caused climate change as opposed to
naturally-occurring cycles? I realize this might go beyond the scope of
your study, but perhaps you have some ideas about this.MANOJ
JOSHI: Well, what we do is we do a combination of things. We look at
climate observations to see if the sorts of things we see are maybe more
common or rarer than they were in the past. And a very important part
of understanding this puzzle, because correlation doesn't necessarily
imply causation, is to look at climate models, which sort of embody our
knowledge of the physics, chemistry, biology of the climate system. And
what we can do with these climate models is we can answer "what ifs." We
can simulate the world as it is with emissions of greenhouse gases
increasing as they are in the 21st century, but we can also run these
climate models without human interference in the climate systems. Say,
"Well, what might the climate be like if you only had natural
variations?" The differences between these two types of model runs can
tell us what the effect of human activity is.GREGORY WILPERT: I
see. A very recent draft UN report warns that we are set to breach Paris
Accords' two-degree Celsius limit by mid-century. And the Climate
Action Tracker, a very reputable MIT-affiliated, non-profit think tank,
sets the current global warming trajectory at "warming to about 3.16
degrees Celsius above pre-industrial levels by 2100," and this is based
on pledges that have been made so far as part of the Paris Agreement. So
would you say we are locked into this warming? Or, with political will,
could this trajectory be still reversed?MANOJ JOSHI: We're
certainly not locked into the sorts of warming you just quoted up to the
year 2100. Whilst there is inertia in the climate system, it certainly
possible that actions we start to take now will start to limit warming
from the mid-century or indeed before. So there are things that can be
done by limiting carbon emissions into the atmosphere. We can certainly
prevent a scenario of, say, three degrees from happening by the 21st
century if action is taken very soon.GREGORY WILPERT: When we
report on potentially catastrophic climate change, there's always the
concern that an audience will think that things are hopeless, and you've
just countered that. But would you say that we are at a crossroads and
that we have a choice to make, a responsibility to put our political
representatives to act now before it is too late?MANOJ JOSHI: I
think the more that carbon emissions are reduced, the lower the
temperature trajectory. As a climate scientist, we make projections that
people then look at to then judge how to basically look at policy, how
to change policy. What individual people need to do in terms of talking
to policy makers and so on is something for individual people. We can
present the evidence, and then it's up to individual people, companies,
communities to make their own decisions on that. As for saying people
should be doing certain things, I myself am uncomfortable about getting
into that. All I can do is present the information, and then people have
to make decisions about what to do, etc.GREGORY WILPERT: Okay.
We'll continue to follow this very closely. I was speaking to Dr. Manoj
Joshi, professor of climate dynamics at the University of East Anglia.
Thanks again for having joined us today, Professor Joshi.MANOJ JOSHI: Thanks for having me.GREGORY WILPERT: And thank you for joining The Real News Network.
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