history of and evidence for climate change Flashcards
1
Q
past variations in carbon dioxide
A
- measured from trapped air bubbles in ice cores drilled in Antarctica and Greenland
- co-vary with temperatures over the last 800,000 years
- temperature measurements from oxygen and hydrogen isotypes in the frozen water in ice cores
- GHGs in atmosphere and global temperatures are closely linked
2
Q
rise in greenhouse gases before the industrial revolution
A
- small rise in GHGs shown from ice core evidence linked to early farmers
- 7,000ya a rise in CO2 starts, possibly from deforestation and land clearing
- 5,000ya a rise in CH4 starts, possibly from expansions of wet rice agriculture and cattle
3
Q
Dip in global temperature anomaly (1960s-1970s)
A
- Global mean surface temperatures decreased
- Some scientists believed that the increases in temperature up to then were also a part of normal temperature fluctuations
- Some scientists had concern about a new ice age period
4
Q
Mauna Loa observatory records
A
- first measurements of CO2 concentrations started in 1958 on the summit of Mauna Loa mountain, Hawaii, remote area, avoids contamination from local pollution sources
- shows an increase from 316 to 424ppm from 1958 to 2015 (from 280ppm pre-industrial ice core data)
- atmospheric CO2 concentration has increased every year since 1958
5
Q
problems with measuring atmospheric CO2
A
- large seasonal variations from variations in uptake from vegetation
- may only show half of CO2 that has been emitted so far, as around half is absorbed by land and ocean sinks (ability of sinks to store carbon may be diminishing)
6
Q
NASA and NOAA studies
A
- tracked increase in CO2 concentration
- tested how CO2 absorbs and reradiates heat
- tracked significant changes in global temperature and sea level
- analysed physical effects on environment and systems
- tracked significant shifts in weather patterns and changes in phenology
- tracked sunspot and volcanic activity to rule them out
- NASA and NOAA proved correlation with different statistical techniques and came up with the same conclusion that natural events could not account for these measured changes
7
Q
measuring change in global temperature
A
- direct thermometer-based measurements, marine air temperatures (MATs), sea surface temperatures (SSTs)
- proxy based indicators e.g. infrared satellite measurements
- past measurements from tree and coral rings, ice cores and SSTs and MATs from ships since the 19th century (patchy and unreliable)
- observed warming of between 1.0C and 1.3C between 1880 and 2020
- land is warming up faster than oceans (land = 1.4C, oceans = 0.9C)
8
Q
measuring change in global precipitation
A
- not as well documented
- some evidence for a global increase in precipitation (positive feedback, water vapour is a GHG)
- latest IPCC report showed significant increases in Northern hemisphere and long term drying trends in Sahel, Mediterranean, South Africa, Southern Asia, heavy rainfall events such as hurricanes have also intensified
9
Q
measuring change in global sea level
A
- sea level measured relative to land with tidal gauges, can be inaccurate due to isostatic change
- also measured by buoys and satellites
- rose over 24cm between 1901 and 2018, around 2mm a year (IPCC)
10
Q
other evidence for climate change
A
- 3.5-4% reduction of Arctic sea ice per decade, fossil record shows extent of ice from border communities
- active layer above permafrost in Siberia increased 7-15% since 1900
- phenological evidence
11
Q
IPCC
A
- intergovernmental panel on climate change
- established in 1988 by UN environmental panel and the world meteorological organisation to address concerns about climate change
- continued assessment on the state of knowledge about climate change and the scientific, environmental and socioeconomic impacts to provide governments with and guide responses
- does not undertake scientific research but brings together key research in IPCC reports
12
Q
Eunice Newton (1856)
A
- studied the greenhouse effect by shining light on flasks containing different gases
- found that when heated with sunlight, CO2 would warm up the flask
13
Q
John Tyndall (1866)
A
- Used thermopiles to measure effects of different gases on the transfer and absorption of heat
- Found that Co2 and water vapour were potent greenhouse gases
14
Q
Svante Arhenius (1896)
A
- Suggested a link between atmospheric Co2 concentration and climate
- Suggested that halving Co2 concentrations would reduce temperatures by 4C
- Hypothesised that this could explain ice ages
- Suggested that doubling Co2 concentration could increase temperatures by 4C
- Hypothesised this could result from the burning of fossil fuels
15
Q
Guy-Stewart Callendar (1938)
A
- Collated data from 147 records around the world to create the first long term series of surface temperature measurements from the previous 50 years
- Showed that the world was warming, and the correlation between rising Co2 and surface temperatures
- Suggested that a doubling of Co2 would cause a 2C warming
- Many scientists were sceptical
- thought these changes would be countered by the oceans
