2.1 Causes of climate change

Question 1

Define climate change

Answer 1

Any long-term trend or movement in climate detected by a sustained shift in the average value for any climatic element (for example, rainfall, drought, hurricanes).

Question 2

What are greenhouse gases?

Answer 2

Atmospheric gases that absorb infrared radiation and cause world temperatures to be warmer than they would otherwise be.

Question 3

Define external forcing

Answer 3

A term used to describe processes that impact Earth’s climate system, which originate from outside of the climate system itself, such as variations in solar output.

Question 4

What are the two reasons why climate change can occur?

Answer 4

-Changing concentrations of greenhouse gases

-External forcing

Question 5

Explain how changing concentrations of greenhouse gases can lead to climate change

Answer 5

-Changing concentrations of greenhouse gases (carbon dioxide, methane and nitrous oxide) affect temperature.

-These greenhouse gases (GHGs) allow sunlight to pass through Earth’s atmosphere but trap the heat that is radiated back towards space (short-wave sunlight is absorbed when it hits the ground, or water, and is later re-emitted as long-wave infrared heat radiation).

-If the concentration of GHG rises above its naturally occurring level, this is the climatic equivalent of putting extra blankets on a bed.

-More heat is retained, resulting in a warmer, more energetic and less predictable climate system.

Question 6

What would the Earth’s temperature be without GHGs?

Answer 6

-18°C (too cold for life to have evolved)

Question 7

Explain how external forcing can lead to climate change

Answer 7

-Various kinds of external forcing may occur.

-This means the amount of sunlight reaching Earth is reduced or increased.

-This may be because of changes in the Sun’s activity or Earth’s distance from the Sun, for instance.

-Any such change in the global energy balance results in a fall or rise in global mean surface temperature (GMST).

Question 8

Diagram showing the greenhouse effect

Answer 8

Question 9

Explain the greenhouse effect (take from other deck?)

Answer 9

1) Solar energy enters the atmosphere.

2) As this short-wave energy passes through the atmosphere, it might hit dust particles or water droplets and be scattered or reflected.

3) Only a little short-wave radiation is abosrbed in the atmosphere.

4) Solar energy heats the Earth’s surface, which then radiates long-wave (heat) energy into the atmosphere.

5) Long-wave energy is quite easily absorbed by naturally-occuring greenhouse gases in the atmosphere. Of these, carbon dioxide is by far the most abundant.

6) Some long-wave energy escapes into space.

Question 10

What are the different pieces of evidence of naturally-occuring climate change over time?

Answer 10

-Fossil and geological records

-Landscape evidence

-Tree rings

-Agricultural records

Question 11

Explain how fossil and geological records can give evidence about naturally-occuring climate change

Answer 11

-Fossils, sedimentary rocks and sediments (containing pollen grains) offer clues about environmental changes over time.

-The geologically recent appearance and later disappearance of woolly mammoths in what is now Europe indicates that periods of cooling and warming occurred in the past.

Question 12

Explain how landscape evidence can give evidence about naturally-occuring climate change

Answer 12

Evidence for past sea-level changes is provided by raised beaches (landforms which show sea level used to be higher than it is today) and drowned valleys called rias and fjords. From these, we surmise that Earth’s ice caps have changed size, along with the volume of water stored in oceans.

Question 13

Explain how tree rings can give evidence about naturally-occuring climate change

Answer 13

-Trees produce one new ring of growth per year, during the growing season.

-A warmer year results in a wider ring.

-Patterns of slower and faster growth can be observed that allow us to estimate temperatures in the past.

Question 14

Explain how agricultural records can give evidence about naturally-occuring climate change

Answer 14

-Historical grape harvest dates have been used to reconstruct summer temperatures in Paris, France, from 1370 to 1879.

-These contribute to our understanding of the so-called ‘Little Ice Age’ (a relatively cold phase from around 1300 to 1850) and the ‘medieval warm period’ (900–1300) that preceded it.

Question 15

In addition to explaining why world temperatures have sometimes risen or fallen, ___ help determine the strength and duration of any changes.

Answer 15

Positive and negative feedback processes

Question 16

What are positive feedback loops?

Answer 16

-They are knock-on effects in natural systems, which act to accelerate and amplify any changes that have already started to occur.

-When one element of a system changes, it upsets the overall equilibrium, or state of balance, thereby leading to changes in other elements that reinforce what is happening.

Question 17

What are negative feedback loops?

Answer 17

-These occurs when a system adjusts itself in ways that lessen or cancel out the effect of the original change.

-In this case, feedback has triggered changes in other elements, which act in the opposite direction from the initial change.

-As a result, equilibrium or balance is restored.

Question 18

Diagram of a positive feedback loop showing a possible way the climate system could respond to more carbon dioxide being added to the atmosphere (for example, as a result of fossil fuel use).

The first scenario suggests accelerated warming as various system changes take place, which strengthen one another.

Answer 18

Question 19

Diagram of a negative feedback loop showing a possible way the climate system could respond to more carbon dioxide being added to the atmosphere (for example, as a result of fossil fuel use).

Answer 19

.

Question 20

Which is more concerning for scientists: positive or negative feedback loops?

Answer 20

-There is widespread concern among the world’s climate scientists that positive feedback effects associated with human emission of carbon dioxide will be far greater than negative feedback effects in the coming decades.

-As a result, there is a significant risk of a high rise in GMST (of 4–6°C) occurring by 2100.

Question 21

What are the different reasons for variations in solar radiation?

Answer 21

-Volcanic emissions and global dimming

-Changes in solar output

-Changes in the Earth’s orbit

-Cosmic collisions

Question 22

Explain how volcanic emissions and global dimming can be a reason for variations in solar radiation

Answer 22

-Major past volcanic eruptions have led to a short-lived period of global cooling lasting for one or two years only.

-This is because of ash and dust particles being ejected high into the atmosphere, blanketing Earth and reducing incoming insolation.

-Mount Pinatubo’s 1991 eruptions caused global temperatures to drop temporarily by about 0.5°C.

Question 23

Explain how changes in solar output can be a reason for variations in solar radiation

Answer 23

-A variety of output cycles have been detected in the amount of energy emitted by the Sun.

-The most obvious of these is an 11-year sunspot activity cycle.

-Sunspots are dark areas where intense magnetic storms are happening, which increase solar output.

-A long period with almost no sunspots lasting from 1645 to 1715 is called the Maunder Minimum.

-It has been linked to the cooler conditions that existed during the Little Ice Age.

Question 24

Explain how changes in the Earth’s orbit can be a reason for variations in solar radiation

Answer 24

-Three known cycles occur in Earth’s orbit around the Sun, resulting in warming and cooling over long periods of time as incoming levels of solar radiation change.

-Firstly, every 100,000 years, Earth’s orbit changes from spherical to elliptical, changing the solar input.

-Secondly, Earth’s axis is tilted at 23.5 degrees, but this changes over a 41,000-year cycle by between 22 and 24.5 degrees, also affecting solar input.

-Thirdly, Earth’s axis wobbles, changing over 22,000 years, bringing further climate change.

-These orbital cycles are usually termed Milankovitch cycles (the theory of astronomical climate forcing was developed by Milutin Milankovitch).

Question 25

Explain how cosmic collisions can be a reason for variations in solar radiation

Answer 25

-Large asteroids colliding with Earth may have caused dramatic, though short-lived, climate change in the past.

-The mass extinction of the dinosaurs is thought to have been caused by a large meteor strike 65 million years ago.

-Its explosive impact would have thrown up an enormous volume of debris.

-A vast dust cloud may have blocked sunlight and prevented photosynthesis for up to 10 years.

-This would have been long enough for the food chains that sustained the dinosaurs to collapse entirely.

Question 26

Define global dimming

Answer 26

-Suspended particulate matter in the atmosphere can reflect solar energy back into space and so have a net cooling effect.

-This phenomenon can occur naturally because of volcanic emissions but can also be caused by human pollution too – meaning that fossil fuel burning may be both warming and cooling the planet at the same time.

Question 27

Graph showing the ineratction between the three Milankovitch cycles

Answer 27

Question 28

Explain the albedo effect

Answer 28

-During periods when Earth has grown warmer in the past, temperature changes may have accelerated because of the loss of ice cover.

-Ice has a high albedo of around 80 percent, which means it reflects four-fifths of all incoming solar radiation.

-If some white-colored sea ice melts in the Arctic, for instance, darker-colored water will be revealed.

-The water has a lower albedo because of its dark color and, consequently, it absorbs more heat.

-As it warms, the water becomes more likely to melt any remaining sea ice.

-This results in the opening up of more areas of the open ocean, and so the process repeats.

-When the water grows warmer, so too do the air masses that are in contact with it.

-The result is accelerated warming of the atmosphere.

Question 29

Define albedo

Answer 29

-How much solar radiation a surface reflects.

-White surfaces have the highest albedo, or reflectivity.

Question 30

How can a positive feedback loop exacerbate the albedo effect?

Answer 30

-This positive feedback process means that even a small change in sea ice coverage can have a significant impact on global climate potentially.

-In theory, even a small reduction in sea ice cover could lead eventually to an ice-free Arctic.

Question 31

How do geologists believe the Earth’s ice cover has changed over time?

Answer 31

-There are periods in Earth’s past when the planet has been entirely ice free; at other times the majority of land has been covered with ice. Geologists believe that:

•Earth may have become a giant ‘snowball’ during two distinct Cryogenian ice ages that occurred around 650 to 750 million years ago

•During much of the Paleocene and early Eocene geological epochs (about 65–35 million years ago), ‘hothouse’ conditions meant the poles were probably free of ice caps.

-Feedback cycles linked with albedo changes occurring both on land and water may have played an important role in producing both outcomes.

Question 32

Give an example of a negative feedback loop in which the climate system could self-correct if Arctic ice began to melt

Answer 32

1)Ice melts to expose the darker ocean which absorbs more sunlight.

2)As the ocean warms, there will be increased levels of evaporation.

3)This will create more cloud, especially in the lower atmosphere.

4) The light-coloured cloud has a high albedo and reflects incoming solar radiation (much as the ice used to).

5) As a result, less light reaches and is absorbed by the ocean surface.

6) The temperature of the water falls, as does that of the air mass in contact with it.

Question 33

Diagram of a negative feedback loop in which the climate system could self-correct if Arctic ice began to melt

Answer 33

Question 34

What is methane?

Answer 34

-A very powerful greenhouse gas, enormous volumes of which are stored in frozen soils in Earth’s permafrost regions.

-Around one quarter of Earth’s surface is affected by continuous or sporadic permafrost, including tundra, polar and mountain regions

Question 35

Explain the relationship between methane and permafrost

Answer 35

-Some researchers estimate that the amount of methane in permafrost equates to more than double the amount of carbon currently in the atmosphere.

-The effects of permafrost melting may also be magnified potentially over time in positive feedback loops.

-In theory, this could take Earth’s climate beyond a ‘tipping point’.

Question 36

What is permafrost?

Answer 36

-Ground (soil or rock and included ice) that remains at or below 0°C for at least two consecutive years.

-The thickness of permafrost varies from less than 1 metre to more than 1.5 kilometres.

Question 37

How much permafrost is there on Earth?

Answer 37

-Globally, permafrost covers 23 million square kilometres (mostly in Earth’s northern hemisphere).

-It formed during past cold glacial periods and has persisted through warmer interglacial periods, including the Holocene (the last 10,000 years).

-However, reports indicate that it is now shrinking at an alarming rate.

Question 38

Describe the evidence that indicates that permafrost is shrinking at an alarming rate

Answer 38

-One estimate shows that the tundra climate zone (where most permafrost is found) has shrunk in size by about 20 per cent since 1980.

-According to scientists at NASA, temperatures in Newtok, Alaska, have risen by 4°C since the 1960s, and by as much as 10°C in winter months.

-Based on current evidence, it is likely that widespread melting of permafrost will have occurred by 2100.

Question 39

Need more info/statistics on climate change?

Question 40

What has the IPCC’s 2013 assessment stated?

Answer 40

-It is ‘virtually certain’ humans are to blame for ‘unequivocal’ global warming.

-Atmospheric concentrations of the greenhouse gases (GHGs) carbon dioxide, methane and nitrous oxide are at levels ‘unprecedented in at least the last 800,000 years’.

Question 41

Why is it believed that humans are to blame for climate change?

Answer 41

-Proof of emissions

-Industrial/agricultural practices

-Carbon dioxide data

Question 42

Proof of emissions as a reason why it is believed that humans are to blame for climate change

Answer 42

-Carbon dioxide emissions have been rising since 1750, the start of Europe’s Industrial Revolution, from a level of 280 ppm (parts per million) to 406 ppm at the start of 2017.

-This represents an increase of around 45 percent.

-Even more worryingly, if you convert other GHGs (methane, nitrous oxide) into their equivalent amounts of CO2, then you find that we have reached a level in excess of 470 ppm of CO2 equivalents).

Question 43

Industrial and agricultural practices as a reason why it is believed that humans are to blame for climate change

Answer 43

This is because population growth and economic development have led to: worldwide use of carbon-rich fossil fuels as an energy source; widespread deforestation; and enhanced methane emissions derived from livestock (bovine flatulence) and the decomposition of organic wastes in landfill sites.

Question 44

Carbon dioxide data as a reason why it is believed that humans are to blame for climate change

Answer 44

-A steep trend line can be viewed in carbon dioxide data: there was gradual growth up to the early 1900s and then very rapid growth.

-Older evidence comes from ‘fossil air’ trapped in ice.

-Permanent ice in high mountains and polar ice caps has built up from snow falling over hundreds of thousands of years.

-Cores 3–4 kilometres long have been extracted from the Vostok ice sheet in the Antarctic, producing ice that is more than half a million years old and containing bubbles of ancient air.

-After analysing the evidence, scientists believe that carbon dioxide and methane concentrations are now higher than at any time in the last 800,000 years

Question 45

The highest polluters in terms of total carbon output are ___

Answer 45

High- and middle-income countries with large populations, including China, the USA, India, Russia, Japan and Germany.

Question 46

What are the three key things to remember when comparing countries (pollution in terms of carbon output)

Answer 46

-Data showing per capita carbon footprints reveal a very different pattern.

-The highest figures belong to oil-rich Middle Eastern states including Qatar and Kuwait.

-The USA and EU countries have relatively high per capita carbon footprints but so too do many Caribbean countries where wood is burned widely.

-China has a relatively low per capita carbon footprint.

Question 47

Define per capita footprint

Answer 47

The amount of carbon dioxide emissions an average person in a country is responsible for as they go about their everyday life.

Question 48

Why might our perception of which countries should be held most to account for anthropogenic climate change alter depending on whether we look at carbon stock or carbon flow data – or both?

Answer 48

-Because current data shows the present-day anthropogenic carbon flow generated by different countries.

-However, data showing which countries are responsible for most of the anthropogenic carbon stock already in the atmosphere reveal a very different pattern; Germany, for example, may be to blame for around 6.9 per cent of all anthropogenic carbon emissions dating back to 1750.

-In 2015, Germany accounted for only 2.3 per cent of current carbon flow.

Question 49

Why is it important to consider globalization and trade when thinking about global patterns of carbon emissions?

Answer 49

-Some high-income countries claim to have reduced their carbon emissions in recent years.

-However, falling domestic emissions mask the fact that many developed countries now import much of their food and consumer goods from other countries since deindustrialization and globalization took place.

-Although they have reduced their own emissions, they have increased their overall carbon consumption through importing energy-intensive goods produced in emerging economies.

-Some people believe countries should be held accountable for the carbon emitted by goods they consume but which were made in other places.

-If we factor in global trade, then a very different pattern of responsibility for climate change emerges.

-Germany’s annual share of global carbon emissions rises to almost 10 per cent, for instance.

Question 50

Define anthropogenic carbon flow

Answer 50

-The current amount of carbon emission released annually by a country (for example, due to fossil fuel burning and cement making) produced in each nation.

-The figure can be adjusted upwards to factor in the carbon equivalents of other greenhouse gas emissions (methane and nitrous oxide).

Question 51

Define anthropogenic carbon stock

Answer 51

The total size of the store of anthropogenic carbon emissions released into the atmosphere since industrialization began around 1750.

Question 52

Define deindustrialization

Answer 52

-The loss of traditional manufacturing industries in some high-income countries due to their closure or relocation elsewhere.

-Since the 1960s, many industries have all but vanished from Europe and North America. Instead, they thrive in Asia, South America and, increasingly, Africa.

Question 53

What role does the USA play in global GHG emissions?

Answer 53

-The USA is the world’s second biggest emitter, generating just under one fifth of all anthropogenic GHGs.

-This is despite its population size being less than 5 per cent of the global total.

Question 54

What action has the USA taken to reduce its GHG emissions?

Answer 54

-In recent years, its carbon emissions have fallen by around 10 percent.

-The main reason for this is a shift from coal to gas burning within the USA’s energy mix.

-A gas-fired plant produces half the emissions of a coal-fired one.

-Under the Obama administration, the USA began taking greater action to address its emissions.

-However, the Trump administration is more skeptical of the need for action.

Question 55

What role does China play in global GHG emissions?

Answer 55

-China became the world’s largest carbon emitter in 2007 on account of widespread industrialization since the 1970s.

-A massive programme of poverty alleviation (requiring more, not less, energy) remains the country’s priority.

-China now contributes around one quarter of world emissions while accounting for one fifth of world population.

-Its emissions rose by almost 10 per cent in 2011 alone, primarily due to higher coal consumption.

Question 56

What action has China taken to reduce its GHG emissions?

Answer 56

-China’s leaders want to reduce the rate at which their emissions rise and have made a (non-binding) pledge to reduce the carbon intensity of the country’s growth by adopting more renewable energy into their mix.

-For instance, China spent US$10 billion on wind turbines in 2010 – about half of all global spending.

-Such actions will not lead to a cut in total emissions but will curb the rate at which China’s emissions grow.

Question 57

What role does India play in global GHG emissions?

Answer 57

-Currently, it contributes more than 5 percent of global CO2 emissions.

Question 58

What role does Qatar play in global GHG emissions?

Answer 58

-The oil-rich desert state of Qatar has exceedingly high per capita emissions.

-The country’s great oil wealth is used to fund high energy usage, including lavish use of air conditioning.

Question 59

What role does Japan play in global GHG emissions and what action have they taken to reduce these emissions?

Answer 59

-Japan’s emissions have increased in the 2010s as a result of a substantial increase in the use of fossil fuels in power generation.

-This is part of a reaction against the use of nuclear power following the accident at Fukushima in 2011.

-However, they have decreased in recent years.

Question 60

What role do low-income countries play in global GHG emissions and what action have they taken to reduce these emissions?

Answer 60

-Many of the world’s least developed countries (LDCs), such as Somalia, continue to make a negligible contribution to anthropogenic GHG emissions, although economic changes in some African countries, such as Nigeria and Kenya, mean that energy consumption there is rising.

-People in some poor countries may have a high per capita carbon footprint because of their reliance on wood-burning stoves as a source of heat and energy for cooking.

Question 61

Define carbon intensity

Answer 61

-The amount of CO2 emitted per unit of GDP.

-If a country’s carbon emissions rise less slowly than its GDP is increasing, this suggests some action is being taken to reduce emissions at the same time as industrial output is increasing.

Question 62

What is renewable energy?

Answer 62

Wind, solar and tidal power sources that result from a flow of energy from the Sun.

Question 63

Why is climate change a ‘wicked problem’?

Answer 63

-There is uncertainty over the operation of feedback loops.

-Nor can we predict with any certainty what kinds of economic and demographic changes will take place globally or in particular countries.

-As a result, climate change presents us with a wicked problem which – because of its complexity – defies attempts to establish exactly what its effects would be.

-Unfortunately, this uncertainty is seized upon by climate change skeptics as a reason to avoid taking any action to reduce GHG emissions.

Question 64

What other factors introduce greater complexity to climate change models?

Answer 64

-Natural climatic cycles like the El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) are independent phenomena that operate naturally on shorter, decade-long timescales.

-They introduce year-to-year climatic variability into numerous different local contexts.

-Both phenomena can bring colder conditions temporarily to places that are predicted to get warmer on account of long-term climate change.

Question 65

How do other factors like the El El Niño Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) further complicate climate change models?

Answer 65

-This complicates our understanding of long-term climate change and can undermine public faith in IPCC expert predictions.

-People who lack deeper scientific understanding of the issues may – quite understandably but erroneously – view one unusually cold winter as ‘irrefutable proof’ that the planet cannot be warming up.

Question 66

What is a ‘wicked problem’?

Answer 66

-A challenge that cannot be dealt with easily due to its scale and/or complexity.

-Wicked problems arise from the interactions of many different places, people, things, ideas and perspectives within complex and interconnected systems.

Question 67

What is the El Niño Southern Oscillation (ENSO)?

Answer 67

-A sustained sea surface temperature anomaly across the central tropical Pacific Ocean.

-It brings a change in weather conditions that can last from two to seven years.

-Along with La Niña events, El Niño events are part of a short-term climate cycle that brings variations in climate but only for a few years.

Question 68

Diagram showing a summary of some of the many different influences on climate change processes and the high levels of complexity and uncertainty that affect future predictions of climatic change

Answer 68

Question 69

In which atmospheric layer does weather take place?

Answer 69

Troposphere

Question 70

The Earth is a ___ system

Answer 70

Closed

Question 71

Explain how ocean currents transfer heat around the Earth

Answer 71

-Surplus energy exists between the tropics and is moved wia wind and water currents

-Ocean currents transfer warm water towards the poles and colder water towards the equator

-Prevailing winds help to drive ocean currents whilst they also transfer hot and cold air masses between places

Question 72

Explain short-wave vs. long-wave radiation

Answer 72

-Short-wave light radiation from the sun hits the Earth’s surface (the soil, rocks and plants, etc.) and is transformed into long-wave heat radiation that eventually escapes into space.

-If some of the heat did not escape the Earth would heat up. For the Earth to maintain its stable temperature the outgoing long-wave radiation must match the incoming short-wave radiation.

Question 73

Explain a human factor that causes global dimming

Answer 73

-Air pollution decreases the amount of sunlight reaching the planet

-This is because aerosols or small particles are formed from pollutants that reflect and absorb radiation

-Subsequently, the radiation is not able to reach the ground

Question 74

Natural gas is ___% methane

Answer 74

90

Question 75

The angle of ___ is highest at the equator

Answer 75

Incidence