quote Originally posted by cliffw: I have asked you before and not even maven rinselberg could answer about what instrument reports [carbon dioxide or CO2] levels. What other color gasses are there? [CO2] is not the largest quantity of gasses. We hear of various level of allergies there are and the quantities. Why is that not true of all the gasses (which are lighter than air) in the atmosphere? Climate mitigation is wearing more clothes, less clothes, using a heater [or] building a fire, running the A/C.

Great questions, as always, from forum member "cliffw".

Let's start with the monitoring of CO2 and other greenhouse gases by direct measurements of air samples:

quote The National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory has measured carbon dioxide and other greenhouse gases for several decades through a globally distributed network of about 70 air sampling sites, including the Mauna Loa Observatory in Hawai’i. The data for this indicator come from a subset of about 40 of these sites located in isolated regions of the ocean.

The "indicator" is a reference to the Annual Greenhouse Gas Index (AGGI) data that NOAA maintains.

It's all explained very succinctly on this NOAA web page:
https://www.globalchange.go...heric-carbon-dioxide


Data from air samples has been augmented by data from earth orbiting satellites; this was published in October 2008:

quote NASA is getting ready to launch a first-of-its-kind satellite that can measure the sources and sinks for carbon dioxide around the planet, in January 2009. The Orbiting Carbon Observatory is an incredible new tool in the global effort to understand climate change that will fill in the gaps left by ground measuring stations in parts of North America, Europe and Asia. The new satellite mission dovetails with a newly-announced plan by Virgin Galactic and the National Oceanic and Atmospheric Administration to measure carbon dioxide concentrations in the upper stratosphere, mesosphere and lower thermosphere with Virgin's high altitude carrier aircraft, White Knight Two, and its spacefaring companion, SpaceShipTwo. The Economist just published a great article on the two new systems that explains how together they might finally offer us the high resolution map of carbon sources and sinks that scientists need to more accurately understand how, where and why carbon dioxide is entering and exiting the atmosphere. The NASA satellite will measure sunlight reflecting off the planet and calculate what gases are present in a 6-mile-wide column of gas to an accuracy of one part per million. Inserted into a polar orbit, the satellite will fly over the polar cap every 16 days, like a string being wrapped around the planet in 6-mile swaths.

"CO2 Monitoring Satellite, Virgin Galactic Team Up"
Loretta HIdalgo Whitesides for Wired; October 7, 2008.
https://www.wired.com/2008/10/carbon-monitori/


The European Space Agency has satellite launches planned for 2026:

quote ESA, the European Commission, Eumetsat and industrial partners are therefore working extremely hard to get the Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission ready for liftoff. . . . The two CO2M satellites will each carry a near-infrared and shortwave-infrared spectrometer to measure atmospheric carbon dioxide at high spatial resolution. These measurements will be used by the new CO2M Monitoring and Verification Support Capacity, which the European Centre for Medium-Range Weather Forecasts is developing, and which will eventually reduce uncertainties in estimates of emissions of carbon dioxide from the combustion of fossil fuel at local, national and regional scales. The two CO2M satellites are scheduled to be launched sequentially in 2026 and are qualified to operate as a constellation for 7.5 years in orbit, with fuel to extend their life to 12 years.

ESA press release; May 23, 2022.
https://www.esa.int/Applica...e_monitoring_mission


It's all based on the "fingerprints" of carbon dioxide; more technically, the Infrared Absorption Spectrum of Carbon Dioxide. (Other greenhouse gases, such as methane, have their own uniquely distinctive IR absorption spectrums.)



Air samples are analyzed for these fingerprints in a laboratory using an Infrared Spectrometer.

An earth-orbiting satellite can measure the IR fingerprints of carbon dioxide and other greenhouse gases with sensors onboard the satellite that capture the infrared sunlight that's being reflected to the satellite from the earth's atmosphere and land and ocean surfaces.

Or going one better (so to speak), an earth-orbiting satellite can be equipped with a "sounder" which uses the LIDAR technique to transmit IR pulses downwards from orbit towards the earth and capture the returns that come back to the satellite as IR reflections from the earth's atmosphere and land and ocean surfaces. The fingerprints of carbon dioxide and other greenhouse gases are the IR absorption lines, and their frequencies and intensities are recovered by computer analysis of the IR reflection data. This is how the European Space Agency's Carbon Dioxide Monitoring Mission or CO2M will be doing it, after the satellites are launched in 2026.




Measuring carbon dioxide and other greenhouse gases from a satellite in polar orbit.

"cliffw", if you're listening...

[This message has been edited by rinselberg (edited 02-11-2023).]