Science and Impacts Flashcards
What is climate?
The average weather (its mean and variability) over a specific time period
What is Climate Change?
The change in climate with time due to natural variability or human activity (IPCC)
Examples of observed climate variables …
Temperature, Precipitation, humidity, cloud cover, snow cover, sea-ice thickness and extend, natural modes (ENSO, NAO)
How are anomalies used?
To identify positive and negative excursions from a start/end point or around a long-term trend
Summary of surface temperature changes
In the 20th century there has been a consistent large-scale warming of the land and ocean surface
Which time period saw the greatest warming?
the last 30-50 years (IPCC, 2013)
When did surface observations of temperature begin?
1880 - use of thermometers
What do radiosondes do?
Measure variables (e.g. temperature, relative humidity, wind speed) at discrete altitudes, transmits to a computer by radio
How do we measure upper air temperature?
Radiosondes and Satellite
What do satellites do?
Measures radiation emitted by earth to get temperature and moisture readings
Why are satellites useful?
Broad coverage … can make up for northern hemisphere bias of surface readings
Upper air temperature trends, relative to the 1981-2010 mean …
- lower troposphere has warmed globally
- lower stratosphere has cooled
What impact do volcanic eruptions have on the troposphere and stratosphere?
Cools the troposphere and heats the stratosphere
How have Arctic temperature trends changed over time?
Average arctic temperatures have increased at almost twice the global average in the past 100 years
What happened to sea ice during the global warming ‘hiatus’?
Arctic sea ice continued to decrease
How have glaciers changed worldwide? The Alps?
Glacier retreat worldwide
-Alps: 500m decrease in length since 1950
What is the North Atlantic Oscillation (NAO)?
A mature of circulation patterns in the northern hemisphere
What does a positive NAO imply?
Warmer European conditions
How have positive NAO indices changed?
Greater occurrence from 1980s-1990s
Climate extremes in the last 50 years …
- more extremely warm days and nights in a year
- fewer extremely cold days and nights in a year
- fewer frost days in mid-latitudes
What causes sea-level rise?
- Thermal expansion
- Ice cap melt
- Isostatic rebound (since ice sheet melt, land recovering, can move up and down)
Which is more straight forward to model-temperature or precipitation?
Temperature
What is the precipitation trend in the higher latitudes?
More precipitation falling as rain, rather than snow
What different indicators do we have to know the world has warmed?
(IPCC AR5)
- Decrease in … glacier volume, snow cover, sea ice area
- Increase in … air temperature, water vapour, land temperature, ocean heat content, sea surface temperature
When was the European heat wave?
2003 … probably the hottest summer in Europe for 500 years
When did European tide gauge measurements begin?
As early as 1670
When did southern hemisphere tide gauge measurements begin?
Late 19th century
What is the issue with tide gauges?
Large gaps in time and geographical spread
When did NASA and NOAA start tracking global ocean topography?
1992
What does satellite altimetry do?
Capture variations in sea level across most of the planets oceans every 10 days
What is the Argo project?
The deployment of floating sensors across the worlds oceans, with 3918 devices present in 2015
How do we measure paleo ocean level?
Proxy records e.g. dating of uplifted fossils
What is the Anthropocene?
Different geological, sociological and anthropogenical changes in recent Earth history (Waters et al., 2016)
What evidence suggests we could be in the anthropocene?
Changes in rock deposits (plastic, “technofossils”), sediment retention behind dams altering delta subsidence, pesticide residue
What has happened with nitrate signatures?
Nitrate levels in the Greenland ice are higher than at any time during the previous 100,000 years
How quickly has Arctic sea ice been receding since 1980?
Over 10% reduction per decade
Since 1880, about how much has global mean sea level risen by?
20cm
Who first coined the term ‘Anthropocene’?
Paul Krutzen
