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CHAPTER 22: MEASURING CLIMATE CHANGE (Climate models and assessing the…
CHAPTER 22: MEASURING CLIMATE CHANGE
Atmospheric greenhouse gas concentrations - a key indicator :red_flag:
There is a direct link btwn atmospheric gas concentrations and climate. The rate and magnitude of these changes in greenhouse gases have significantly influenced the Earth's climate system.
Ancient climate change
Result of natural forces: volcanic eruptions, Milankovitch cycles, solar flares, weathering f silicate rocks, limestone formation, photosynthesis rates and decomposition of plant and animal matter.
Earth experienced another four major glacial-interglacial cycles. - The Earth has had warm periods and cooler periods when it was covered in ice.
Recent Changes
The human-induced climate change is occurring at a rate ten to twenty times faster than those caused solely by non-human causes.
Without the impact of human activities, the Earth would be currently in a fairly stable pattern of glacial and interglacial periods as it has experiences over hundreds of thousands of years.
Even with these natural changes, over the past 800,000 years, global atmospheric concentrations of CO2, methane and nitrous oxide have not been as high as today's levels.
Measuring Changes in the atmosphere
Ice Core Samples :star:
Cylinders of ice drilled out of an ice sheet or glacier; they reveal info about past temps and many other aspects of the enviro.
The ice contains small bubbles of air that contain a sample of the atmosphere as it was when the ice formed, providing us with the opportunity to measure the past conc of gases - mainly CO2 and CH4 - in the atmosphere. The ratio of oxygen 16 to oxygen 18 isotopes in the water molecules provide info on past temps.
Most ice core records from Antarctica and Greenland; the oldest continuous ice core records extend back 123000 years in Greenland and 800000 yrs in Antarctica. The longest ice core extends 3km down.
Scientists compare modern data with past temps and conc of CO2 and methane from layers in ice cores.
Before industrial emissions started, atmospheric CO2 sat at approx 280 ppm. Over the preceding 10000 years, CO2 conc varied between 180 -300ppm.
Palaeobotany :smiley:
The study of plant life of the geoIogical past. Identify the kinds of plants that grow in a given area, from which the kind of climate prevailed at the time can be inferred.
Use plant fossils, or impressions of plant parts preserves in sedimentary rocks, coal or other geological deposits.
One method of mapping the plant distribution over time is to study the pollen left in lake sediments by wind-pollinated pants that once grew in lake's vicinity.
Sediment in the bottom of lakes; as they tend to be laid down in annual layers.
Plants are generally distributed across the landscape based on temperature and precipitation patterns, plant communities change as these climatic factors change. By knowing the conditions that plants prefer, conclusions can be made about the past climate.
Scientists can infer the climate of the layer being studied by relating it to the current climatic preferences of the same plants.
Atmospheric and Ocean temperatures :star:
Both are linked and influence each other.
The ocean is a major heat sink, and sea surface temperature is a critical indicator of climate change.
Major ocean currents move water, and the heat contained in that water, around the globe, affecting climate on a regional to global scale.
Observing its changes over both short-term and long-term timeframes provide vital info about past climate change, for understanding the present climate and for input into predictive climate models.
Recorded by: direct measurements from weather stations on land and on water and remotely by thermal and microwave imaging sensors on satellites.
Evidence of changing surface temp come from analysis of long-term temp records, studies of ocean temp records, studies using balloon borne sensors and surface and satellite observations of stratospheric cooling.
Climate models and assessing the rate of climate change
Sophisticated mathematical representations of the climate that stimulate the interactions of the important drivers of climate, including processes in the atmosphere and oceans, and on the land surfaces and ice sheets.
Vital for understanding global climate change and generating global climate models that allow us to predict future outcomes.
An uncertainty in the model is the extent to which global warming will be delayed by the thermal capacity of the ocean and any possible changes to ocean circulation.
Another uncertainty in predicting the impact of greenhouse gases if the effect of the particles in the atmosphere, especially those formed from sulphur compounds emitted by industry.
STUDY DESIGN
Measurements that give useful information about changes in the climate
• methods used for measuring and understanding past and present changes in the atmosphere: ice core samples, paleo-botany, atmospheric and ocean temperature monitoring, climate models
magnitude and rate of change in individual atmospheric gas concentrations over different time periods
(seasonally, annually and over millenia) due to natural events and human actions, including exponential increase in CO2 post-industrial revolution.
• measures used to assess the rate of climate change: global average annual temperatures, regional and global sea level rise, and global snow and ice coverage.