Ecology: climate changes Flashcards
What is the difference between weather and climate?
- Weather: the combination of temperature, humidity, precipitation, wind, cloudiness and other atmospheric conditions that occurs in a specific place and time
- Climate: the average long-term trend of
weather, and can be local, regional or global
What determines the climate?
- Atmosphere
- Position and inclination of the earth
- Earth rotation
What does the atmosphere consist of?
78.08% nitrogen
20.95% oxygen
0.93% argon
0.04 % carbon dioxide
It regulates the temperature - greenhouse effect (without atmosphere – 18°C)
What is the difference in wavelength radiation between the sun and the earth?
- Sun emits shortwave radiation (avg surface temp = 5800 °C)
- Earth emits (relative) longwave radiation (avg surface temp = 15 °C)
What is net radiation?
The difference between the amount of
(solar) shortwave radiation absorbed by a surface and the amount of longwave
radiation emitted by the surface into space.
Earth heat budget
Earth is a balanced ecosystem in term of solar energy inputs and
outputs
Global map of net annual radiation
Intercepted solar radiation varies with…
- Latitude
- Season
Why does intercepted solar radiation vary with latitude?
At high latitudes, radiation hits the surface
at a steeper angle, spreading sunlight over
a large area.
Also radiation travels through a deeper layer of air, reflecting more back to atmosphere.
Why does intercepted solar radiation vary with the season?
Earth’s axis is tilted at an angle of
23.5oC. It is this tilt that is responsible
for the seasonal variations in T and
day length.
How does variation in solar radiation cause large variations in temperature seasonally and daily?
- The differences in the intensity of solar radiation reaching the earth’s surface generate temperature differences
- Which, together with the effects of the earth’s rotation, originate winds and ocean currents
by convection (i.e. the process of heat transfer from one location to the next by the flow of fluids from a high temperature location to a low
temperature location). - These, in turn, influence the distribution of
precipitation, and play a crucial role in transferring heat from the equator to high latitudes
Relationship between air temperature and density
- Air, like most other substances, expands
when heated and contracts when cooled. - Because there is more space between the
molecules, hot air is less dense than the surrounding matter and it floats upward.
What happens to the temperature when air moves upward?
The temperature decreases due to adiabatic cooling
Why is the temperature a vertical gradient?
Vertical temperature gradients due to:
- Greater air density near the surface
(collision between molecules generates heat) - “Warming effect” of the earth’s surface
- Adiabatic cooling (caused by gas
expansion as pressure decreases)
Which 2 factors generate the circulation of air masses?
- Changes in air temperature
- Earth’s rotation
What is the coriolis effect?
- Deflection in the pattern of air flow.
- Clockwise movement in N hemisphere,
counterclockwise in S. Hemisphere.
(Three cells and trade wind belts, see picture)
Which factors generate ocean currents?
- Solar energy
- wind
- earth’s rotation
Ocean currents
- Ocean currents also affect climate, sometimes very dramatically (source of energy movement too)
- Each ocean is dominated by great circular water movement, or gyres. Gyres move
clockwise in the N. Hemisphere and counterclockwise in the S. Hemisphere
(Coriolis effect). - Warmer water moves away from equator and cold water moves towards equator.
What is also generated by solar energy, wind and the earth’s rotation?
Preciptation patterns
Relationship between air moisture and temperature
What do the latitudinal patterns of precipitation follow?
- The circulation cells.
- The peaks in precipitation correspond to the rise in air masses such as that of the
Intertropical Convergence Zone;
-Vice versa the depressions are associated with the descent of the water masses
Global pattern of precipitation
Wind, temperature and ocean currents determine the global distribution of precipitation
What influences regional and local patterns of precipitation?
Topography
What is an example of irregular variations in climate at regional scale?
- El Niño Southern Oscillation (ENSO); a periodic shift of the ocean-atmosphere system in the tropical Pacific that impacts weather around the world.
- It happens every 3-7 years (5 years
on average) and typically lasts nine months to two years. - It is associated with floods, droughts, and other global disturbances.
What is ENSO?
El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature (El Niño) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean.
What are normal (non-El Niño) conditions?
- Trade winds blow west across the Pacific, piling up warm surface water so that the sea surface is about one-half meter higher around Indonesia than around Ecuador.
- Ocean upwelling occurs off the coasts of Peru and Ecuador.
- The western equatorial Pacific is characterized by warm, wet, low-pressure weather, typhoons and thunderstorms.
What happens during ENSO?
- Trade winds slacken (verslappen), reducing the westward flow of the surface currents.
- Rainfall follows the warm water eastward, with associated flooding in Peru and drought in Indonesia and Australia.
What happens during La Niña?
- The east to west flow present during neutral conditions is intensified,
- Injection of cold water becomes more intense than usual, causing the surface of eastern Pacific to cool.
- Results in droughts in South America and heavy rainfall in Australia.
What are micoclimates?
- Defines the local, small scale conditions in which
organisms live. - These conditions include:
topography (aspect=direction a slope
face), light, temperature, air conditions or wind
movement, moisture etc.
What is the Intergovernmental Panel on Climate Change (IPCC)?
- The leading international body for the assessment of climate change.
- It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988.
- Thousands of scientists from all over the world contribute to
the work of the IPCC on a voluntary basis.
Why was the IPCC established?
To provide the world with a clear scientific view on the current state of knowledge in climate change and its potential environmental and
socio-economic impacts.
Temperature increase (as an observed change in climate)
- Human influence has warmed the climate at a rate that is unprecedented in at least the
last 2000 years. - The likely range of total human-caused global surface temperature increase from 1850–1900 to 2010–2019 is 0.8°C to 1.3°C, with a best estimate of 1.07°C
Where is the observed warming the strongest?
Observed and projected warming are stronger over land than oceans and strongest in het Arctic.
Changes in annual preciptation (as an observed change in climate)
Globally averaged precipitation over land has likely increased since 1950, with a faster rate of increase since the 1980s (medium confidence)
Changes in precipitation patterns (as an observed change in climate)
CNR Data - tropicalization of rainfall regimes in Italy:
- on average total rainfall has only slightly decreased
- the number of rainy days has decreased
- the intensity of precipitation per day has increased
- causing both severe droughts and floods
Ocean warming (as an observed change in climate)
Ocean warming dominates the increase in energy stored in the climate system, accounting
for more than 90% of the energy
accumulated between 1971 and
2010 (high confidence).
It is virtually certain that the global
upper ocean (0−700 m) has warmed
since 1970s
Global surface mean temp anomalies
Melting glaciers ((as an observed change in climate)
Mountain glaciers are decreasing, due to:
- increase in temperature
- decrease in rainfall
Sea ice thickness (picture)
N. Hemisphere spring snow cover vs Arctic summer sea ice extent
Sea level rise ((as an observed change in climate)
- The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence).
- Over the period 1901 to 2010, global mean sea level rose by 0.19 [0.17 to 0.21] m
Why is sea level rising?
Global mean sea level budget since 1993
Ocean acidification (as an observed change in climate)
Carbon dissolves in water
Carbon - bicarbonate equilibrium
Proportions of the forms of CO2 in relation to PH
- CO2 additions or losses affect the pH and
changes in pH determine the prevailing form in
which CO2 is present
What is the pH of sea water?
Sea water is slightly alkaline, with a pH between 7.5 and 8.4
How do CO2 emissions cause ocean acidification?
- Carbon dioxide concentrations have increased by 40% since pre-industrial times,
- primarily from fossil fuel emissions and secondarily from net land use change emissions.
- The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide,
- causing ocean acidification.
Relation surface ocean CO2 and pH
What are the changes in extreme events since the 1950’s?
- It is almost certain that hot extremes have become more frequent and more intense across most land regions
-Cold extremes have become less frequent and less severe,
- With high confidence that human-induced climate change is the main driver of these changes
- Some recent hot extremes observed over the past decade would have been extremely unlikely to occur without human influence on the climate system.
What about the changes in marine heatwaves?
- They have approximately doubled in frequency since the 1980s (high confidence)
- Human influence has very likely contributed to most of them since at least 2006.
What are the changes in frequency and intensity of heavy precipitation events since the 1950’s?
- They have increased since the 1950s over most land area (high confidence)
- Human-induced climate change is likely
the main driver. - Human-induced climate change has contributed to increases in agricultural and ecological droughts in some regions due to increased land evapotranspiration (medium confidence).
Increase in drought and heat between 1982-2011 (map)
Definition of a marine heatwave
- Marine Heat Wave is defined as a discrete prolonged anomalously warm water event.
- “Discrete” means an identifiable event with recognizable start and end dates
- “Prolonged” implies a duration of at least 5 days
- “Anomalously warm” measures temperatures relative to a baseline climatology and threshold
What is evapotranspiration?
The sum of all processes by which water moves from the land surface to the atmosphere via evaporation and transpiration
What about changes in wave power?
There has been an increase in global wave power
What about changes in storm hazards?
- Storm hazards are rising
- It is likely that the global proportion of major (Category 3–5) tropical cyclone occurrence
has increased over the last four decades - it is very likely that the latitude where
tropical cyclones in the western North Pacific reach their peak intensity has shifted
northward; - these changes cannot be explained by internal variability alone (medium confidence).
What about the changes in natural disasters?
- They are more frequent than 30 years ago - and are costing us more
Summary table of observed changes in extremes
Drivers of climate change
- Emissions from human activities
- Increase in well-mixed greenhouse gas (GHG) concentrations
Emissions from human activities (As a driver of climate change)
- Observed warming is driven by emissions from human activities,
- with greenhouse gas warming partly masked by aerosol cooling
What is aerosol cooling?
- When the sky is clear (devoid of clouds), aerosols can reflect incoming sunlight back to outer space – the direct effect.
- This blocks part of the energy that would have reached the surface, thus having a cool effect on the climate
Increase in well-mixed greenhouse gas (GHG) concentrations
(As a driver of climate change)
- Increases since 1750 are unequivocally caused by human activities.
- Since 2011 (measurements reported in AR5), concentrations have continued to increase in the atmosphere
- Land and ocean have taken up a near-constant
proportion (globally about 56% per year) of CO2 emissions from human activities over the past six decades, with regional differences (high confidence).
Global average GHG concentrations (graph)
What were the annual averages of GHG in 2019?
- CO2: 410 parts per million (ppm)
- Methane, CH4: 1866 parts per billion (ppb)
- Nitrous oxide, N2O: 332 ppb
Graph showing glacial - interglacial data
Greenhouse gas emissions in the year 2000 (graph)
What are the 2 main climate change predictions?
*Global surface temperature will continue to increase until at least mid-century under all emissions scenarios considered.
*Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.
Future emissions scenarios
Graph with different scenarios:
- SSP5-8.5: very high GHG emissions
- SSP3-7.0: high GHG emissions
- SSP2-4.5: intermediate GHG emissions
- SSP1-2.6: net negative GHG emissions
- SSP1-1.9: net negative GHG emissions
Global temperature change under the different emissions scenarios.
Comparing the years 1850-1900 to the years 2081- 2100 in global temperature:
The temp. will rise by:
- 1.0°C to 1.8°C (SSP1-1.9)
- 2.1°C to 3.5°C (SSP2-4.5)
- 3.3°C to 5.7°C(SSP5-5.8)
The global average temperature will increase by 1 – 5.7°C in this century
When was the last time surface temperature was at 2.5°C or higher than in 1850-1900?
3 million years ago
Table of estimates of changes in temperature with their confidence level
Global warming of 2°C, relative to 1850–1900, would be exceeded during the 21st century under the high and very high GHG emissions scenarios
3 maps of temperature change scenarios
Sea warming estimates for the mediterranean
The Mediterranean is predicted to also gain salinity as warm tropical water flows in from the
Red Sea
Overview of what changes in the climate system become larger in direct relation to increasing global warming
- Increase in frequency and intensity of hot extremes, marine heatwaves, heavy precipitation, and agricultural and ecological droughts
- Increase in proportion of intense tropical cyclones
- Reduction in Arctic sea ice, snow cover and permafrost
What does every additional 0.5°C of global warming cause?
Clear increases in intensity and frequency of:
- hot extremes
- heavy precipitation
- agricultural and ecological droughts
Maps of projected changes of marine heatwaves (MHWs)
Date of the first permanent MHW and proportion of ocean with permanent MHW
Evolution of global mean MHW days (graph)
Increased drought risk
- Discernible (waarneembare) changes in intensity and frequency of meteorological droughts, with more regions showing increases than decreases
- seen in some regions for every additional 0.5°C of global warming (medium confidence).
Map of increase of drought risk in Europe
Changes in precipitation with global warming
- Very likely that heavy precipitation events will intensify and become more frequent in
most regions - At global scale, extreme daily precipitation events are projected to intensify by about 7% for each 1°C of global warming (high confidence).
- The proportion of intense tropical cyclones (Category 4–5) and peak wind speeds of the most intense tropical cyclones are projected to increase at the global scale with increasing global warming (high confidence).
Precipitation scenarios
Ice melting scenarios
- Mountain and polar glaciers are committed to continue melting for decades or centuries (very high confidence).
- Loss of permafrost carbon following permafrost thaw (ontdooien) is irreversible at centennial time scales (high confidence).
- Continued ice loss over the 21st century is virtually certain for the Greenland Ice Sheet and likely for the Antarctic Ice Sheet.
- There is high confidence that total ice loss from the Greenland Ice Sheet will increase with cumulative emissions.
Project sea level rise scenarios by 2100 and 2150
Relative to 1995–2014, the likely global mean sea level rise by 2100 is:
- 0.28–0.55 m under the very low GHG emissions scenario (SSP1-1.9);
- 0.32–0.62 m under the low GHG emissions scenario (SSP1-2.6);
- 0.44–0.76 m under the intermediate GHG emissions scenario (SSP2-4.5);
- 0.63–1.01m under the very high GHG emissions scenario (SSP5-8.5);
And by 2150:
- 0.37–0.86 m under the very low scenario (SSP1-1.9);
- 0.46–0.99 m under the low scenario (SSP1-2.6);
- 0.66–1.33 m under the intermediate scenario
(SSP2-4.5); - 0.98–1.88 m under the very high scenario (SSP5-8.5)
Global mean sea level rise relative to 1900 (graph)
Global mean sea level rise in 2300 relative to 1900
Projected increase in flood risk
- At present there are about 40 million people exposed to coastal flooding in the next 100 years
- Like the one which occurred in New Orleans in 2005 following hurricane Katherina.
- 40 million people and > US$3,000 billion exposed assets who are concentrated in cities in India, Bangladesh, USA, China, Egypt, The Netherlands, Vietnam, Thailand, Japan, Indonesia and also many other regions in Europe.
- And by 2070s, the total population exposed could grow more than threefold to around 150 million people,
- due to the combined effects of climate change, subsidence, population growth and urbanisation
Future flood hazards (graph)
Low Elevation Coastal Zone (LECZ) here defined as the contiguous and hydrologically connected zone ofland along the coast and below 10 m of elevation
Map of flood risk in Europe
How is the flood risk exacarbates (verergerd) by coastal erosion?
- Natural factors: strorm surge, waves, currents, sea level rise, river watershed changes
- Anthropogenic factors: dams, coastal infrastructures, sandmining, land subsidence,
loss of coastal vegetation.
What percentage of sandy beaches around the world are recessional?
70%
Erosion of coastline in Europe
- > 15,000 km of coastline actively retreating,
- some of them despite of coastal protection projects (2,900 km)
- another 4,700 km are artificially stabilized
Erosion of coastline in the US
- Around 86% of the east coast barrier beaches have experienced some erosion during the past 100 years.
- Widespread also in California and Gulf of Mexico
Erosion of coastline in China
Erosion over one-third of the coastline
(≈46% of the Bohai Sea, 49% of the Yellow Sea,
44% of the East China Sea, and 21% of the South
China Sea (Cai et al 2009)
What is/ has been the most common approach to coastal erosion and disaster prevention?
Hard engineering.
- Europe > 2900 km of coastal protection armouring
- China’s new “Great Wall,” covers 60%
of the total length of coastline along
mainland China
Projected acidification scenarios
Projected increase in anoxic events
How do warming waters cut oxygen?
- Increasing stratification of the ocean and weakening the overturning circulation of the water
- Decreasing oxygen solubility
- Combined with excess nutrients from land they cause harmful algal blooms which drain oxygen as they die and decompose
What happens to the proportion of CO2 emissions taken up by land and ocean carbon sinks, when CO2 emissions increase?
The proportion is smaller in case of a CO2 emission increase.
