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Cloudy climate change. How clouds affect earth's temperature
Earth's average surface temperature has warmed by point eight celsius since 1750
when carbon dioxide concentration in the atmosphere have doubled
which is expected before the end of the twenty first century
Researchers project global temperature will have raisen by 1.5 to 4.5 degrees Celsius
if the increase is near the low end 1.5 celsius
then we're already half way there
we should be more able the adopt with some regions are becoming dryer and less productive
but others becoming warmer wetter and more productive
on the other hand, a rise of 4.5 degree celsius would be similar in magnitude
to the warming that's occur since the last glacier maximum, 22 thousand years ago
when most of the north America was under ice sheet 2 kilometer's thick
so that would represent the dramatic change of climate
so it's vitally important for scientists to predict the change in temperature
with as much precision as possible. so the society can plan for the future
the present range of uncertainty simply too large to be confident of how best to respond to climate change
but this estima to 1.5 to 4.5 celsius for doubling the carbon dioxide hasn't change in 35 years
why haven't we been able to narrow it down?
the answer is we don't yet understand aerosols in clouds well enough
but the new experimentists is tackling the problem
in order to predict how the temperature will change. Scientist need to know some called earth climate sensitivity.
the temperature change in response to radiative forcing
A radiat forum set is a temperate imbalace between the energy receive from the sun
and energy radiate back out to space like the imbalance cause by increase of green house gases
to correct imbalance of warms up or cools down,
we can determine earth climate sensitivity from the experiment we've already performed in industrial age since 1750.
and then the uses number to determine how much more it will warm to varies projected radiated forcing in the twenty first century
to do this, we need to know two things.
First, the global temperature rise since 1750.
And second, the radiative forcing of the present day climate relative to the pre-industrial climate
for the radiative forcing we know that human activities has been increased green house gases in the atmosphere which warm the planet
but our activities have at the same time increase the amount of aerosols particles in clouds which have cooled the planet.
Pre-industrial green house gas concentrations are well measured
From bubbles trap in ice course of tent in Greenland and Antarctic.
So the greenhouse gas forcings are precisely known.
But we have no way of direct recongnition how cloudy it was in 1750.
And that’s the main source of uncertainty in earth climate sensitivity.
To understand pre-industrial cloudy is we must use computer models
that reliably simulate the process is responsible for forming nuclei in clouds.
Now, to most people aerosols are the things to make your hair stick.
But that’s only one type of aerosols.
Atmospheric aerosols are tiny liquid or solid particles suspended in the air.
There are either primary from dust sea spray salt, burning biomass
Or secondary formed by gas to particle conversion in the atmosphere
Also known as particle nucleation.
Aerosols are everywhere in the atmosphere. And they can block out the sun and polluted urban environments.
Or bath distant mountain in blue pace.
More importantly the cloud droplet cannot form without an aerosol particle seed.
So without aerosol particle, there’ll be no clouds.
And without clouds, there will be no fresh water.
The climate will be much hotter. And there will be no life.
So we owe our existence to aerosol particles.
However, despite their importance how aerosol particles form in the atmosphere
aren’t very effect on clouds and poorly understood.
Even the vapor is responsible for aerosol particle formation and not well established.
Because at present in only might mute amount near one molecule per million million molecules are there.
This lack of understanding is the main reason for the large uncertainty in climate sensitivity.
And the corresponding wild range of future climate projections.
However, an experiment under way is certain named surprisingly cloud has manage to build a steel vessel
That’s large enough and has low enough contamination that aerosol formation can
For the first time, be measured under tightly controlled atmosphere condition in the bar of tray.
In the first five years of operation, cloud has identified the vapor
responsible for the aerosol formation in the atmosphere.
Which includes sulfuric acid, ammonia amines and biogenic vapours from trees.
Using an eye and icing particle bean for the certain proton synchrotron
Cloud is also investigating if galactic cosmic rays enhance the formation of aerosols in clouds.
This has been suggested as possible unaccounted natural climate forcing agent
since the flux of cause midgrade raining down in the atmosphere.
There is with solar activity.
So cloud is addressing two big questions:
Firstly, how cloudy was the pre-industrial climate?
And hence, how much have clouds changed due to human activities?
That knowledge will help sharpen climate projections in the 21st century.
And simply, could the puzzling observation of solar climate variability in the pre-industrial
be explained by an influence of galactic cosmic rays on the clouds?
Ambitious but realistic goals, when your heads in the clouds



【TED-Ed】 雲朵氣候學:雲朵如何影響地球氣溫? Cloudy climate change: How clouds affect Earth's temperature - Jasper Kirkby

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Go Tutor 發佈於 2014 年 11 月 21 日
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