Climatologists had been expressing concern over the damage to the carbon cycle from increased anthropogenic emissions caused by human activities, mainly from the burning of fossil fuels and altered land use.
Authored by Kenneth Richard, a new study points to the rise of Carbon Dioxide by 110 ppm since 1750 in which human contribution is just 17 ppm.
Taking an alternative approach to that of IPCC on carbon dioxide uptake by natural sinks such as plants, ocean, and soil the paper says uptake increases as a proportion to the expansion of carbon dioxide concentration. The study also makes a strong case for clubbing natural emission with temperature changes and absorption rates for assessing the concentration of the greenhouse gas.
Industrial Era Carbon Surge
The new study infers that anthropogenic contribution to carbon dioxide concentration is only 4.3 percent and the surge in carbon dioxide during the Industrial Era was just 15 percent.
The study says it will be an impossible proposition as maintained by IPCC that there will be an uptake of 15 - 40 percent of carbon dioxide by photosynthesis and gas exchange.
The IPCC says carbon dioxide emitted until 2100 will linger in the atmosphere longer than 1000 years and removal of human-emitted CO2 from the atmosphere will be used up by natural processes and the process will take many centuries.
The paper mentions that the IPCC data on the carbon cycle is heavily tilted to fossil fuel emissions, land use change, or cement fabrication, ignoring changes in the natural emissions that contribute 95 percent of the total emissions.
The study says the average carbon dioxide residence time in the atmosphere also varies and it is not constant as reflected in the IPCC values.
Temperature Factor
It cites investigations by Humlum or Salby for a strong linkage between the emission rate of natural carbon dioxide and surface temperature.
The core difference with IPCC and the study is in emission and absorption rate. The study says uptake does not saturate and keeps rising as a proportion to the actual concentration in the atmosphere.
The interpretation also led to forming a new residence time of carbon dioxide concentration in accordance with the total emission rate.
It asserts that the natural emissions contribute 373 parts per million (ppm) and human-made anthropogenic emissions are adding just 17 ppm to make a total concentration of 390 ppm with an average residence time of carbon dioxide being 4 years.
New Variables Considered
The paper justifies the figures considering the exponential decay of 14C. It says the surge in carbon dioxide concentration from the Industrial Era till date has more to with temperature change that affected natural emission rate and residence time is also connected to temperature.
It says IPCC's reasoning of the steep increase in concentrations must factor in processes including degassing of the oceans, growth of plants and vegetation, and a higher residence time caused by the decreasing solubility of carbon dioxide in the seas.
The study says all the upward surges of carbon dioxide concentration during the Industrial Era are not anthropogenic emissions but natural emissions also contributed substantially to it. It justifies the hypothesis on the ground that carbon dioxide changes trail temperature changes.
Emissions Flat
Meanwhile, 2016 was the third successive year when global carbon oxide emissions stayed flat. A new study, however, cautions that it is too early to cheer as similar declines are unlikely to translate into gains without corresponding advances in carbon capture and storage with a more push toward renewable energy.
"The good news is that fossil fuel emissions have been flat for three years in a row," said Robert Jackson, chair of the Department of Earth System Science at Stanford's School of Earth, Energy & Environmental Sciences.
However, Jackson noted that actual reductions in global emissions are required, and it hinges on careful tracking of emission pledges and country-level statistics are required.
In the effort to cut down greenhouse gasses, technologies that can capture atmospheric carbon and store them underground are required. More push on renewables such as wind and solar can also help.
If such steps are not taken seriously, the world may miss the temperature target set by the Paris Agreement and the goal of net-zero climate pollution.
The study published in Nature Climate Change evaluated the progress in emission pledges of 150 nations who are signatories to the Paris Agreement with pledges to keep global warming below 2 degrees Celsius of pre-industrial levels.
