1.13: Past, Present and Future Climates II – 21st-century climate futures (Prof. M. Beniston – UNIGE)

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來自 University of Geneva 的課程

Climate Change and Water in Mountains: A Global Concern

18 個評分

University of Geneva

Climate Change and Water in Mountains: A Global Concern

18 個評分

What is climate change ? How are mountain regions affected by the evolution of water resources and their uses ? What kind of risks need to be considered ? Mountains are recognized as particularly sensitive physical environments where intense and rapid changes have in the past, and may increasingly in the future, place pressure on their resource base. In this context, a team of roughly 100 experts worked from 2008 to 2013 for the European ACQWA project (www.acqwa.ch) which was coordinated by the University of Geneva. The primary objectives of the project were to assess the impacts of a changing climate on the quantity and quality of water originating in mountain regions, particularly where snow- and ice melt represent a large, sometimes the largest, streamflow component. A further objective of the project was to determine the potential disruptions to water-dependent economic activities related to the climate impacts on hydrological systems, and to propose a portfolio of possible adaptation strategies. This particular MOOC is inspired by the ACQWA Project and offers a better understanding of climate change, its impacts on the quality and quantity of water in mountain regions and the risks related to changing water resources. From an interdisciplinary perspective, the participation of twenty-five instructors from five different countries (Switzerland, England, South Korea, India and Nepal) and fourteen institutions (UNIGE, RTS, UNIFR, UZH, ETHZ, Meteodat GmbH, WGMS, Imperial College London, Agroscope, République et Canton de Genève, Yonsei University, IHCAP, ICIMOD, SDC, FOEN) highlights the diversity of both theoretical and practical viewpoints related to these issues. By the end of this course, you will be able : - to define the general concept of climate change in mountain regions - to understand the concepts associated with climate change such as adaptation and water governance strategies - to consider the impacts of climate change on water resources in mountain regions - to identify the impacts of climate change on hydropower, agriculture, aquatic ecosystems and health - to enumerate risks that can occur in mountain areas and lead to disruptions in water availability and use. Your acquired knowledge will be evaluated through multiple-choice quizzes at the end of each unit of the course. This MOOC on “Climate Change and Water in Mountain Regions : A Global Concern” was initiated and financed by the University of Geneva, through its Institute for Environmental Sciences. We look forward to you joining us !

從本節課中

Unit 1: Introduction to climate change

In this module, you will learn about the functioning of the climate system, in particular the numerous interacting components such as the atmosphere, the oceans, the cryosphere and the biosphere. Physical mechanisms that can disrupt climate on different time and space scales will be outlined, and the concepts underlying anthropogenic climate change will be introduced. Following a brief overview of how climate simulation models function, you will be able to see what may be the evolution of climate over coming decades in response to increases in greenhouse-gases in the atmosphere, and what are the limits and uncertainties to these model projections.

1.12: Past, Present and Future Climates I – 20th-century observed change (Prof. M. Beniston – UNIGE)4:08

1.13: Past, Present and Future Climates II – 21st-century climate futures (Prof. M. Beniston – UNIGE)6:55

1.14: Past, Present and Future Climates III – Extreme climate events (Prof. M. Beniston – UNIGE)11:20

1.15: Forecast in Switzerland in 50 years – In summer (Mr. P. Jeanneret – RTS)3:02

與講師見面

Martin Beniston
Honorary Professor
Institute for Environmental Sciences
Markus Stoffel
Full Professor
Institute for Environmental Sciences

So we saw in the second module,

why there is a link between the quantities of

greenhouse gases in the atmosphere and certain levels of temperature in the atmosphere.

What we're going to see now is how climate might actually evolve in coming decades.

So, in order to look at the future evolution of climate,

based on different forms of human activity,

whether it's industrial or agricultural activities,

we need to have available to us what we call climate models.

These are based on the physics of the Earth system,

computer-based models that try to reproduce as faithfully as possible

the different elements of the climate system that I mentioned right at

the start of this particular part of the Mooc.

That is to say, the interactions between the oceans and the atmosphere,

ice and the oceans,

ice and the atmosphere, and so on.

Not only do we need physically-based climate models,

we also need to know something about the way societies will be evolving in the future.

Because the quantities of greenhouse gases that humans will

be injecting into the atmosphere over coming years and coming decades,

will depend upon a number of factors.

Amongst these, we would have demographics,

what will be the size of the world's population in the next 50 or 100 years,

what will be the typical economic growth in different regions,

and what will be some of the technological choices we

might make in terms of the energy sector, for example.

Will we continue to rely upon fossil fuels as much as we have in

the past or will we try to invest more heavily in renewable energy technologies?

For example. So, when we try to

estimate what will be the future course of greenhouse gases in the atmosphere,

we need to try and guess what will be the subtle links between demographics,

economic growth, technological drive, basically,

what will be our societal choices in coming years and coming decades.

So, rather than try and guess just one future trajectory,

scientists have come up with about 40 different scenarios that can be

summarized in this table in the form of four major families of scenarios.

One which is in the upper left part of the of the graph,

shows a world in which we would not change very much our collective behavior,

we would still continue to rely heavily on fossil fuels.

So, we wouldn't be changing very much in that sense.

So, this would translate into a very strong response of the climate system.

Because by putting in more and more greenhouse gases into

the atmosphere related essentially to fossil fuels,

then of course the climate system will warm more rapidly than if we

control the amounts of greenhouse gases that we put into the atmosphere.

And then, on the bottom right corner,

you have the so-called 1.5 degree policy,

that was negotiated in Paris during the COP 21 negotiations in December 2015.

Now, if we implement fully the terms of the Paris agreement,

then we could theoretically limit future warming to 1.5°C,

which of course would have a number of advantages in the sense that the impacts related

to climate change would be much less severe than in a sort of business as usual world,

which would be represented in the upper left corner of this diagram.

Now, using different scenarios and using climate models,

what we can do is try and simulate what the response of climate would be

to one or more of these particular greenhouse gas emission scenarios.

So, now you see in this animation,

one of the climate models that was used in

the evaluations of the Intergovernmental Panel on Climate Change,

the IPCC, that has fed the scientific information to the negotiators of

the Climate Convention and in particular the COP 21 accord in Paris, in December 2015.

And on this animation,

you see that as we move into the future over the coming decades.

You see again, as we saw a few minutes ago with

the animation of the real world from the 19th Century to today,

you see that the warming is by no means uniform.

It's going to be modulated by the distribution of continents and oceans.

It's going to be modulated by the presence or absence of vegetation,

the presence or absence of ice,

and snow on the continents and so on.

But by the end of the 21st Century,

what you see is a general warming taking place.

It will be fairly strong in certain regions,

maybe anything up to 10 degrees more than today.

Now, if 10 degrees more than today sounds a rather exaggerated figure,

I just like to remind you that if you think about the 2003 heatwave in Europe,

for example, we had temperatures that exceeded in certain parts of France and

Western Europe up to 12 degrees more than the average August temperatures.

So, this is the kind of world that we're going to move into.

In other words, what can be considered to be an extreme climate today,

might actually become the average climate of tomorrow.

Now, when we think about climate change,

we think above all of temperature change,

but many other elements of the climate system will also

be modified because of the changes in atmospheric temperatures,

and in particular precipitation regimes will be

modified in response to the enhanced greenhouse effect.

On this animation, which is a very similar model to

the one we saw previously for temperature change,

you see a very noisy picture in terms of

the response of precipitation patterns to the enhanced greenhouse effect.

You see some parts of the world which will dry out compared to today,

and you'll see other parts of the globe where

precipitation is likely to increase with respect to today.

On average, we can say that

the equatorial region might experience more rainfall than today.

The dry zones may experience less rainfall than today,

which is very unfortunate for the populations living in these arid and semi-arid regions.

And the mid to high latitudes are likely to experience

more rainfall or more precipitation than currently.

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