Solar radiation enters the Earth's atmosphere freely and should normally leave as heat. Unfortunately, this is being hampered by the growing "greenhouse roof" of carbon dioxide and other gases.
That is why the Earth is warming and our climate is changing. Infrared measurement devices, known as pyrgeometers, are used to continuously measure the extent of the greenhouse effect.
These measurements' long-term reliability has now been significantly improved.
This was made possible by calibrating the pyrgeometers with a new PTB reference device described in the current issue of Metrologia.
Measuring The Greenhouse Effect Accurately
WILLIAM WEST/AFP via Getty Images
The greenhouse effect is measured by the atmospheric longwave downward radiation, which is the radiation reflected back to Earth from the "greenhouse roof," as per Phys.org.
It has been measured continuously for years using pyrgeometers located on Earth. These infrared measurement devices cover a wide spectral band, capturing a wide range of wavelengths.
They also have a very wide field of view, allowing them to monitor almost the entire hemisphere of the sky.
Pyrgeometers must be regularly calibrated, i.e., metrologically traced to standards, to ensure the informative value and comparability of measurement data over time.
The new reference blackbody, known as the "hemispherical blackbody" (HSBB), is an example of such a standard.
It was created at PTB in collaboration with the Physikalisch-Meteorologisches Observatorium Davos / World Radiation Center (PMOD/WRC) as part of the European "Metrology for Earth Observation and Climate" series of research projects (MetEOC).
The HSBB meets the specific requirements for such calibrations and is traceable to the International Temperature Scale ITS-90 through the PTB's Radiation Temperature Scale and thus to the SI, the International System of Units.
With this, a second independent type of traceability procedure is now available in addition to the one used by PMOD/WRC, which was previously based on contact thermometry and optical simulations.
At the same time, the agreement between the PMOD/WRC and PTB radiometric scales for irradiance serves to validate the previously established traceability.
Discrepancies in previous global measurements of atmospheric longwave downward radiation can now be ruled out, and this radiation can now be measured more precisely.
Take advantage of many utilities' free home energy audits, as per NPS.
Then put the suggestions into action. Installing a programmable thermostat to replace your old dial unit, or sealing and insulating heating and cooling ducts, can each reduce a typical family's CO2 emissions by about 5%.
Replace single-paned windows with dual-paned windows and install insulated doors to reduce heat loss from your home.
More than half of the electricity produced in the United States is generated by polluting coal-fired power plants.
And the single largest source of heat-trapping gas is power plants. Fortunately, alternative energy sources such as solar, wind, geothermal, and hydro energy are gaining popularity around the world.
In Denmark, for example, wind energy provides about 10% of the country's total energy needs. Once operational, these energy generation methods produce no greenhouse gases.
The concept of carbon offset is straightforward: you decide you don't want to be responsible for accelerating climate change, and you've already made efforts to reduce your carbon dioxide emissions, so you pay someone else to further reduce your net emissions by planting trees or adopting low-carbon technologies.
Every unit of carbon absorbed by trees-or not emitted as a result of your support for renewable energy deployment-offsets the emissions caused by your use of fossil fuels.
In many cases, particularly in developing countries, funding renewable energy, energy efficiency, or tree planting can be a relatively inexpensive way of becoming "carbon neutral."
