5.6 Climate change and the hydrological system Flashcards
What are the different components of the hydrological system that may vary due to climate change?
-oceans
-ice
-snow
-permafrost
-reservoir lake and wetland storage
-groundwater flow
-run-off and steam flow
-soil moisture
-evapotranspiration
-precipitation input
How will climate change vary the precipitation input?
-mode of precipitation is important- more will now fall as rain rather than snow
-widespread increases in intense rainfall but overall amount of water stays the same
-precipitation increases in the tropics and high latitudes, but there’s decreases 10-30 degrees n/s of the equator. Similarly, intensity of heatwaves has increased drought risk here
How will climate change vary evapotranspiration?
-transpiration rates are now subject to vegetation changes, soil moisture and precipitation. It increases exponentially as vegetation becomes more productive
-In Asia and North America, evaporation is increasing but increased cloud cover from increased vapor may work against this
How does climate change affect snow?
Length of snow season has now decreased and spring melt has occurred earlier, accelerating in the last decade
How does climate change vary soil moisture?
Where precipitation increases so does soil moisture. Results are ambiguous however as it’s linked to many factors
How does climate change vary run off and stem flow?
a 1 degree rise in temps could increase global runoff by 40%
There will be more hydrological extremes, with more low flows (droughts) and high flows (floods)
An accelerated cycle with more intense rainfall will increase run off rates and reduce infiltration. There are marked decreases in continental Mediterranean, Africa and SW US
How does climate change vary groundwater flow?
no clear influence as human abstraction is the dominant influence
How does climate change vary reservoir lake and wetland storage?
wetlands are affected when there is less rainfall and higher temperatures. Changes are happening to wetlands but they aren’t conclusively due to climate change.
regional variation are linked to regional changes in climate, e.g. Lake Chad
How does climate change vary permafrost storage?
higher temps at higher latitudes lead to permafrost degradation. With the deepening of the active layer, this has an impact on groundwater supplies and also releases methane from thaw lakes, accelerating change
How does climate change vary ice storage?
-glaciers have retreated globally since the end of the little ice age
-downwasting (thinning of glacier ice) accelerating in most areas since the 1970s
-result from increasing temperature and changing precipitation type
-high altitude glaciers have shown rapid changing, leading to cryosphere loss
How do oceans change because of climate change?
-warmer oceans mean more evaporation, but evidence for more cyclones is limited
What are some of the factors linking to a diminishing water supply and increased uncertainty
-less snow and glaciers threaten mountainous communities
-ENSO is leading to less predictable patterns
-Increased intensity and frequency of drought
-More frequent monsoon and cyclones
-depleted aquifers
-decreasing rainfall
-greater rates of evapotranspiration due to heat increase
When were the last strong El Nino events?
97-98 and 2015-16
When were the last strong la nina events?
07-08 and 2010-11
What will happen to the UK weather in the UK by 2100 if carbon emissions aren’t decreased?
The risk of winter flooding will increase by 4 and a half times and the risk of summer drought by 3 times
What is rainfall like in the Sahel?
the amount of rainfall varies from 100mm to 600mm per year, but it has significantly decreased since 1970.
Up to 90% of its annual rainfall is between July and September
What was rainfall like in the Sahel in the 70s and 80s
it failed- with a decline in rainfall of up to 40% of the 50s and 60s
What were the effects of drought in the Sahel in the 70s and 80s?
Drought, poverty an civil war especially in Eritrea and Ethiopia, drove many people onto marginal land. Many died of famine
How many people in California are affected by the changing patterns of rainfall?
40 million
What happened in 2014 in Sierra Nevada?
they experienced three times the number of average wildfires, because the ground was so dry
What are climate scientists predicting for California?
intense mega-droughts, lasting 30 years
What happened to California in 2015?
Marked the 4th year of continuous drought - the worst in 1,200 years- and water rationing was imposed on cities
What are the forecasts now saying about the likelihood of drought in California
50% chance of mega drought a 90% chance of decade long drought
What was drought like for Arizona, California, Nevada, New Mexico, Oklahoma and Texas between 2000 and 2015?
Eleven of the 15 years were drought years and these states have an equal size population to the UK
What are the causes of drought in California and surrounding states?
-rising temperatures have led to an increase in evaporation rates
-fall in precipitation
What evidence shows there are already problems in California?
-surface runoff and soil moisture levels have declined
-forested areas have returned to scrub and grassland
-groundwater levels have fallen by 30m between 2011 and 2015
-Reservoir levels have fallen
-snowpack levels at record lows
By how much have groundwater levels fallen?
In October 2016, water storage was 77% of the average for the time of year- but levels varied. Lake Cachuma was down to 9%
Describe the decrease in snowpack in California
they were at record lows in 2015 due to high temps and a lack of winter storms. Snowpack is crucial because its meltwater provides one third of the water used by California’s farms and cities
How will climate change effect ENSO?
-increase their duration and intensity
What does computer modelling show about how greenhouse emissions will affect the planet?
-different regions of the world will warm at different rates
-La Nina and EL Nino will become more extreme
-regions bordering the Pacific will see flood seasons following drought seasons
By how much does the moisture holding capacity of the atmosphere increase per degree Celsius of global warming?
7%
