Sir David Attenborough: The Truth About Climate Change

Summary

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Mindmap

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Keywords

💡Global Warming

Global warming refers to the long-term increase in Earth's average surface temperature due to human activities, primarily the emission of greenhouse gases such as carbon dioxide. In the video, Sir David Attenborough discusses the distinction between natural climate variations and those induced by human activity, highlighting global warming as a significant concern. The script mentions an 'upward trend' in temperatures around 1910, which is a key indicator of global warming.

💡Natural Causes

Natural causes of climate variation include factors like volcanic eruptions and solar output, which can influence Earth's climate. The video script describes how these natural causes can lead to temporary climate changes, such as a downward trend associated with a volcano. However, the script contrasts these with human-induced changes, emphasizing the need to understand the difference.

💡Human Activity

Human activity, particularly the burning of fossil fuels, is identified as a major contributor to climate change in the video. The script explains that when human factors, especially the greenhouse effect from carbon dioxide emissions, are included in climate models, they accurately reproduce the rapid warming observed in recent decades, indicating that human activity is a primary driver of current climate change.

💡Climate Model

A climate model is a scientific tool used to study the interactions of the atmosphere, oceans, land surface, and ice. The video script describes how climate models are used to simulate the effects of natural and human factors on the climate. The models help to demonstrate that while natural factors can explain some climate variations, they fail to account for the rapid warming seen since the 1970s, which is then attributed to human activity.

💡Greenhouse Effect

The greenhouse effect is a natural process that warms the Earth's surface. However, human activities have intensified this effect by increasing the concentration of greenhouse gases in the atmosphere. In the video, the greenhouse effect is highlighted as a key human factor causing global warming, with carbon dioxide emissions from burning fossil fuels being a major contributor.

💡Volcanoes

Volcanic eruptions can have a cooling effect on the climate by releasing dust and gases into the atmosphere, which can block sunlight. The script mentions that the climate model includes the impact of volcanoes, showing how they can cause temporary downward trends in temperature, contrasting with the long-term warming trend attributed to human activity.

💡Solar Output

Solar output refers to the energy emitted by the Sun, which can influence Earth's climate. The video script includes solar output as one of the natural factors in the climate model, indicating that variations in the Sun's energy output are considered in climate science, but they are not the primary cause of the recent rapid warming.

💡Mid-Century Warming

The mid-century warming refers to a period of climate change observed around the middle of the 20th century. The script describes how climate models can reproduce this warming by including natural factors, suggesting that the mid-century warming could be explained by natural variability. However, the models also show that natural factors alone cannot account for the more recent and rapid warming.

💡Observed Temperatures

Observed temperatures are the actual measurements of Earth's temperature over time. In the video, the red curve represents the observed temperatures, which show a divergence from the model predictions that only include natural factors. This divergence indicates that something else, later attributed to human activity, is causing the temperatures to rise beyond what natural factors alone can explain.

💡Natural Variability

Natural variability refers to the natural fluctuations in Earth's climate system, such as oscillations and trends caused by internal processes and external forces like solar activity and volcanic eruptions. The video script discusses how the climate is 'naturally variable,' with occasional downward trends due to volcanic activity, but these variations are distinct from the long-term warming trend caused by human activity.

Highlights

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Transcripts

the passionate eye now returns to the

truth about global warming for the first

time legendary broadcaster Sir David

Attenborough speaks out about global

warming the key question of course is

how can we distinguish between

variations due to natural causes and

those variations of the climate that are

induced by human activity and the key

thing that convinced me at any rate was

a graph like this one that we marked out

on the floor that had been prepared from

climate scientists like Professor Peter

Cox now explain to us the significance

of this graph ok what we're going to do

is to take a walk through time and the

first thing to note as we walk through

is that the climate is naturally

variable it's a spiky beast occasionally

there's a downward trend that's

associated with a volcano going off the

corsa system down because of the dust it

throws up but generally it just

oscillates around and then we get to a

period around about 1910 where you can

start seeing upward trend a warming of

the climate and global warming if you

like and the issue is what caused that

was that humans or was that natural so

what we do to try and work that one out

is to take a climate model and to put in

the various factors and what we can see

with its green curve here is a climate

model that includes just these natural

factors so this is when volcanoes go off

and the output from the Sun and you can

see that the green curve can reproduce

reasonably well this mid-century warming

so up to this point you could reasonably

argue climate variation can be explained

by natural factors but as we move on we

can see that's no longer true as you get

to the latter part of the 20th century

from about 1970 onwards here

you can see the red curve the observed

temperatures and the green curve really

beginning to diverge and the question

again is what caused this recent warming

so we run the model again and we include

human factors particularly we include

the greenhouse effect from mostly from

carbon dioxide that comes

possibly burning and then we get this

yellow curve and we can see as well as

reproducing the mid-century warming we

get this recent rather rapid warming

reproduced and that tells us two things

one is that the model looks realistic it

looks like the real world and the second

thing the model tells us that this

recent warming is due to human beings so

there you have it the seems little doubt

that this recent rise is steep rise in

temperature is due to human activity if

you look at the green line of natural

variability it's clear that without the

action of human beings there would have

been far less temperature change since

the 1970s