Unit 4 - Climate Change and
Energy Policy
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PHY 305
Climate Change
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PHY 305
Human emissions of carbon dioxide and
other greenhouse gases – are a primary
driver of climate change – and present
one of the world’s most pressing
challenges.
This link between global temperatures
and greenhouse gas concentrations –
especially CO2 – has been true
throughout Earth’s history:
Increase in CO2 and GHG → Increase
in global temperatures
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NASA uses the period from
1951-1980 as a baseline to
see how global temperature
changes over time.
Collectively, the past eight
years are the warmest years
since modern recordkeeping
began in 1880.
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❑ To set the scene, let’s look at how the planet has
warmed. In the chart we see the global average
temperature relative to the average of the period
between 1961 and 1990.
❑ The red line represents the average annual
temperature trend through time, with upper and
lower confidence intervals shown in light grey.
❑ We see that over the last few decades, global
temperatures have risen sharply — to
approximately 0.7℃ higher than our 1961-1990
baseline. When extended back to 1850, we see
that temperatures then were a further 0.4℃ colder
than they were in our baseline. Overall, this would
amount to an average temperature rise of 1.1℃
(0.4 ℃ + 0.7 ℃ )
❑ Because there are small year-to-year fluctuations
in temperature, the specific temperature increase
depends on what year we assume to be ‘pre- Ensure Access to Affordable, Reliable,
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industrial’ and the end year we’re measuring from. Sustainable, and Clean Energy for All
But overall, this temperature rise is in the range of
1 to 1.2℃. ) (Reference period 1850–1900 to represent pre-
industrial temperature) 5
Greenhouse gas emissions from human activities are the main driver of this warming!
How much of the warming since 1850 can be attributed to human emissions? Almost all of it. The
Intergovernmental Panel on Climate Change (IPCC) states clearly in its most recent assessment report:
“Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by
economic and population growth, and are now higher than ever. This has led to atmospheric
concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last
800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected
throughout the climate system and are extremely likely to have been the dominant cause of the
observed warming since the mid-20th century.”
Impacts of Climate Change:
A changing climate has a range of potential ecological, physical and health impacts, including extreme weather
events (such as floods, droughts, storms, and heatwaves); sea-level rise; altered crop growth; and disrupted
water systems.
Ensure change
The most extensive source of analysis on the potential impacts of climatic Access tocan
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in the 5th
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Intergovernmental Panel on Climate Change (IPCC) report. Sustainable, and Clean Energy for All
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https://www.ipcc.ch/report/ar5/wg2/
❑ When we think about the problem of global warming, a
temperature rise of 1℃ can seem small and
insignificant. However, IT IS NOT!
❑ A 1℃ increase in global temperature leads to the rapid
warming of the earth which will not only have
significant impacts on climate and natural systems, but
also this 1℃ figure masks the large variations in
warming across the local countries globally.
In the map shown – taken from the Berkeley Earth global
temperature report – we see the global distribution of
temperature changes in 2019 relative to the period 1951 –
1980.
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Local temperatures in 2019 relative to the average temperature
in 1951-1980 7
Firstly, the global average temperature rise is usually
given as the combined temperature change across both
land and the sea surface. But it’s important to note that
land areas change temperature, both warming and
cooling much more than oceanic areas.
Overall, global average temperatures over land have
increased around twice as much as the ocean.
❑ Compared to the 1951 – 1980 average, temperatures
over land increased by 1.32 ± 0.04 °C.
❑ Whereas the ocean surface temperature (excluding
areas of sea ice) increased by only 0.59 ± 0.06 °C.
→ Since the Northern Hemisphere has more land mass,
this also means that the change in average temperature Ensure Access to Affordable, Reliable,
north of the equator has been higher than the south. Ensure Access
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Secondly, from the map shown, we see that in some
regions the temperature change has been much more
extreme.
At very high latitudes – especially near the Poles – warming
has been upwards of 3°C, and in some cases exceeding
5°C. These are, unfortunately, often the regions which could
experience the largest impacts such as sea ice, permafrost
and glacial melt.
Note: One of the key reasons more warming occurs at high latitudes is
the absence of convection at high latitudes. Convection occurs when air
close to the ground is heated by the warm surface of the Earth. The warmed
air is lighter than the cold air above and so starts to rise.
Monitoring the average global temperature change is
important, but we should also be aware of how differently
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this warming is distributed across the world. In some Ensure Access to Clean
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regions, warming is much more extreme. Sustainable, and Clean Energy for All
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Environmental, Ecological, and Human Effects
of Global Warming
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PHY 305
1- Changes in River Flow (
Droughts)
With a continuation of global warming,
and reductions in snow cover are
anticipated to accelerate throughout the
twenty-first century.
This will reduce water availability and
hydropower potential, and change the
seasonality of flows in regions supplied
by meltwater from major mountain
ranges (e.g.,Hindu-Kush, Himalaya,
Andes), where more than one-sixth of
the world population currently lives
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2- Rise in Sea Level
The sea level reached a minimum during the most recent glacial
maximum.
Since then, the sea level has risen slowly. Sea level rises from two
causes:
(1) Liquid water expands as it warms;
(2) Ice sheets on land that melt increase the amount of water in the
oceans.
Since the end of the last ice age, the sea level has risen approximately
23 cm (about 1 foot) per century. Climatologists forecast
that global warming could about double that rate.
Various models predict that the sea level may rise anywhere from 20 cm
to approximately 2 m (8–80 in) in the next century; the most likely rise is
probably 20–40 cm (8–16 in).
Direct Impacts on Populations:
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About 50 million people each year experience flooding due to storm surges. AsSustainable,
the sea level rises
and and
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increases, more and more people become vulnerable to coastal flooding. The rising sea level particularly threatens island
nations and could worsen coastal erosion on open beaches, making structures more vulnerable to damage from waves.
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How much did the sea
level rise in relative to
the 1993-2008 average
sea level?
→ 9-10 cm
How much did the sea
level rise in relative to
year 1880?
→ Approximately of 25
cm increase
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Glaciers and Sea Ice
The amount of ice on the
Earth’s surface changes in
complicated ways. A major
concern is whether global
warming will lead to a great
decline in the volume of
water stored as ice, especially
because melting of glacial ice
raises the mean sea level.
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North Pole
South Pole
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3- Changes in Biological Diversity
Some of the greatest uncertainties about the consequence of global
warming have to do with changes in biodiversity.
This is because organisms are complex and so their responses to change
can be complex. Warming is one change, but others—such as availability
of nutrients, relations with other organisms (predator and prey), and
competition for habitat and niches in ecosystems—also affect biodiversity
On the other hand, black guillemots, birds that nest on Cooper Island, Alaska,
illustrate the concerns some scientists have about global warming and certain
species.
The abundance of this species has declined since temperature increases in the
1990s caused the sea ice to recede farther from Cooper Island each spring.
The parent birds feed on Arctic cod found under the sea ice and must then return
to the nest to feed their chicks, who are not yet mature enough to survive on their
own. For the parents to do this, the distance from feeding grounds to nest must
be less than about 30 km, but in recent years the ice in the spring has been
receding as much as 250 km from the island.
As a result, the black guillemots on the island have lost an important source of Ensure Access to Affordable, Reliable,
food. The future of black guillemots on Cooper Island depends on future Ensure Access
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springtime weather. Too warm and the birds may disappear in search for food; Sustainable, and Clean Energy for All
Too cold and there may be too few snow-free days for breeding, in which case
they also will disappear.
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4- Wildfires
Increasing heat, changing rain and
snow patterns, shifts in plant
communities, and other climate-
related changes have vastly increased
the likelihood that fires will start more
often and burn more intensely and
widely than they have in the past
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The Mediterranean has become a wildfire
hotspot. In the summer of 2021, the region
was hit by its most intense fires on record
and a heatwave producing a high risk of
further fires and smoke pollution around
the region.
In the summer of 2021, wildfires raged in
Lebanon, Greece and Turkey, where
thousands of people have been evacuated
from their homes
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https://zoom.earth/ Live wildfires map
Global emissions have
NOT yet peaked
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PHY 305
To stabilize (or even reduce)
concentrations of CO2 in the
atmosphere, the world needs to
reach net-zero emissions. This
requires large and fast reductions
in emissions.
Are we making progress towards
this? How far are we from this
target?
At a time when global emissions
need to be falling, they are in fact
still rising, as the chart here
shows. The world has not yet
peaked.
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Those that have access to
energy produce
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high
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Some countries have scaled up nuclear power and renewables and are
doing much better than the global average. You can see this if you change
the chart to show the data for France and Sweden – in France 92% of
electricity comes from low carbon sources, in Sweden it is 99%.
The consequence of countries doing better in this respect should be that
they are closer to the sustainable energy world of the future. The scatter
plot above shows that this is the case.
But for the global energy supply – especially outside the electricity sector –
the world is still far away from a solution to the world’s energy problem.
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