Pledges to cut greenhouse gas emissions are very welcome – but accurate monitoring across the globe is crucial if we are to meet targets and combat the devastating consequences of global warming.
Many countries participated at COP26 in Glasgow. set out their targetsTo reach net zero by the middle century
A report in the Washington Post. It showed that many countries might be under-reporting their emission, with a gap between actual emissions to the atmosphere and what is being reported by the UN.
This is a problem. If we are not certain about our current emissions, we will not be able to know for sure if we have met our future emission reduction targets.
Countries must comply with international guidelines for reporting emissions. These reports are based on “bottom-up” methods, in which national emissions are tallied up by combining measures of socioeconomic activity with estimates on the intensity of emissions involved in those activities. If you know the number of cows in your country and the amount of methane produced by each cow, you can calculate the total methane emissions from all those cows.
There are internationally agreed guidelinesThese guidelines outline how accountancy should be performed, and there is a system for cross-checking to ensure that it is being done correctly.
The Washington Post article reveals that there are unexpected differences in emissions between countries.
There are also significant differences in reporting expectations between countries. Each year, all developed countries must provide detailed and comprehensive reports. However, developing countries are able to report less often due to the administrative burden.
Notable gaps exist in terms of reporting. For example, the potent greenhouse gases that were responsible for the depletion of the stratospheric ozone layer – such as chlorofluorocarbons (CFCs) – are not included.
A ‘top-down’ view from the atmosphere
Scientists have been working hard to address these problems by developing sophisticated techniques that use atmospheric greenhouse gases observations to track emissions. This “top-down” view measures what is in the atmosphere, and then uses computer models to work backwards to figure out what must have been emitted upwind of the measurements.
An international team of scientists met in Glasgow to demonstrate the technique. carbon dioxide and methaneDuring the COP26 conference, things have changed.
While this approach cannot provide the level of detail on emission sectors (such as cows, leaks from pipes, fossil fuels or cars) that the “bottom–up” methods attempt, scientists have demonstrated that it can show whether the overall inventory for a particular gas is accurate or not.
The UK was the first country (now one of three) to publish top-down emissions estimates in its annual. National Inventory Report To the United Nations
A network of five measurement sitesThe UK and Ireland constantly monitor the levels of the main greenhouse gases in the atmosphere using tall towers located in rural areas.
The Met Office has developed computer models that allow us to estimate emissions. These results have been extremely informative.
Recent research showed that the reported downward trend of the UK’s methane emissionsThe atmospheric data shows a similar trend to the last decade. However, a large drop in methane emissions before 2010 is not shown in the atmospheric data. This suggests that the record was over-estimated earlier.
Another finding was that the UK had been over-estimating emissionsFor many years, car air conditioners have been using a potent greenhouse gaz. These studies are discussed with UK inventors and used to improve future inventories.
While countries are not required to use top down methods for their reporting, most recent guidelinesA new version World Meteorological Organisation initiativeAs a best practice, I recommend their use.
There are many challenges to overcome if we want to move from just three countries that have their emissions analyzed in this manner to a global system.
Satellites could be part of the solution. Satellite observations have been available from space for over a decade. They provide data on carbon dioxide and methane which are the most important greenhouse gases. The technology has improvedIt has been a significant improvement in this regard, to the point that it is now possible to image individual methane plumes using orbit.
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Satellites, however, are unlikely to provide sufficient information by themselves.
Space-based and ground-based measurements will both be necessary to create a global emission monitoring system. The cost to establish ground-based systems such as the UK’s will be somewhere between one million and tens of millions of dollars per country per year.
This amount of funding seems possible considering that billions have already been pledged for climate protection projects. If the end result is better emissions reporting and a better understanding about how well we are meeting our emission targets, then such expenditures seem like a great value for money.
It will be up the UN and global leaders for the UN to ensure that the international systems for measurement and top-down emission evaluation can be scaled-up in order to meet the needs of a monitoring system that meets these requirements. Future claims of emission reductions will not be accurate if there aren’t reliable emissions data from multiple sources.