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By Aayushi Sharma
India ranks fifth among the top 10 contributors to the climate crisis, according to a new study. India contributed 4.8% to the global mean surface temperature, while the USA topped the list with a 17.3% contribution. The research paper titled “National contributions to climate change due to historical emissions of carbon dioxide, methane, and nitrous oxide since 1850” was published in the Nature Journal last Wednesday. This study reported national contributions to global warming due to emissions of gases, disaggregation to fossil, and various land use sectors. This dataset will be updated annually in response to the updates of national emissions datasets.
According to the study, historical emissions of greenhouse gases such as carbon dioxide, methane, and nitrous oxide contributed to India’s share. Since 1850, the following countries have contributed the most to global warming: the United States (0.28°C); China (0.20°C); Russia (0.10°C); Brazil (0.08°C); India (0.08°C) while Indonesia, Germany, the United Kingdom, Canada and Japan each contributed 0.03-0.05°C.
According to their findings, CO2 is responsible for 1.11°C of warming, methane is responsible for 0.41°C, and nitrous oxide is accountable for 0.08°C. Furthermore, the United States topped the list of countries, contributing 0.28°C (17.3%) of the temperature rise. China came in second with 0.20°C (12.3%) warming, followed by Russia with 0.10°C (6.1%), Brazil with 0.08°C (4.9%), and India with 0.08°C (4.9%). (4.8 percent). Indonesia, Germany, the United Kingdom, Canada and Japan contributed 0.03-0.05°C to global warming. Since 2005, India has risen from tenth to fifth place. China has also surpassed Russia to take second place.
Gases in focus: Carbon dioxide, methane and nitrous oxide
Since the pre-industrial period, anthropogenic emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) have been significant contributors to climate change. The use of fossil carbon sources in the transportation, energy, industry, waste, and product use sectors, as well as land use, land use change, and forestry (LULUCF), has resulted in increased CO2, CH4, and N2O concentrations in the atmosphere and driven the earth’s surface energy balance into surplus. In its Sixth Assessment Report (AR6), the Intergovernmental Panel on Climate Change (IPCC) estimated that rising atmospheric concentrations of CO2, CH4, and N2O have already caused global mean surface temperature (GMST) to increase by 1.4 °C (0.9-2.2 °C at the 90% confidence interval) in the industrial era, independent of other greenhouse gases (GHGs), ozone precursors (e.g., VOC, CO, NOx), and aerosols (e.g., SO2, black carbon, and organic carbon)
Because of their long-term or powerful climate effects, national CO2, CH4, and N2O emissions are heavily regulated by the United Nations Framework Convention on Climate Change (UNFCCC).
All convention parties set CO2 targets in the form of nationally determined contributions (NDCs), with approximately 90% of NDCs including targets for CH4 and N2O. As a result, keeping track of CO2, CH4, and N2O emissions, as well as the climatic responses to those emissions, is critical for ensuring accountability with regard to NDCs. The current work aims to inform the UNFCCC’s 2023 Global Stocktake, the formal process by which national progress on NDCs is assessed. While we focus on three CO2 emissions, CH4 and N2O, which are included in most NDCs, we note that future research should seek to include other important GHGs, such as fluorinated gases (F-gases), which are also included in some countries’ NDCs.
What is the significance of global mean surface temperature? How is it calculated?
Global warming does not necessarily signify rising temperatures everywhere at the same rate every time. The earth’s temperatures might increase by a few degrees in one region and drop by a few degrees in another. Likewise, the extent of warming may differ in different land masses and ocean surfaces. The global temperature primarily depends on the energy our planet receives from the Sun and the energy radiated back into space. Global mean surface temperature (GMST) is calculated every year. One way to calculate the mean temperature of an entire planet is as follows:
Firstly, the temperature above the land and the ocean in thousands of regions worldwide is measured. Temperature anomaly is then calculated by recording the temperature at regular intervals. When this data is recorded for a year, the plant is divided into grids of 2,592 squares. Secondly, the average of all the temperatures from these 2,592 grids for 265 days is taken. The result is the average of all temperature anomalies from all over the earth which is then compared with other years.
“By focussing on the three gases that most countries include in their Nationally Determined Contributions, this dataset is uniquely positioned to informing climate policy and benchmarking,” said Matthew Jones, Tyndall Centre for Climate Change Research, University of East Anglia.
Some important findings of the study:
- The study estimated that since 2005, China occupies the second position ahead of Russia based on its evolving emissions since 1850. India rose from tenth to fifth position ahead of Indonesia, Germany, the UK, Canada and Japan.
- Thus, a greater fraction of the warming is caused by CH4.
- Emissions associated with land use, land use change, and forestry (LULUCF) were over 60% in India, Australia, Brazil, and Pakistan.
- LULUCF is responsible for 30% of the global warming caused by total CO2 emissions between 1851 and 2021. The contribution of LULUCF CO2-related warming to total CO2-related warming in Russia and India is around the global value. In contrast, the LULUCF share of CO2-related warming is lower in the US (18%) and China (12%) and higher in Brazil (85%) and Indonesia (83%).
- CH4 and N2O emissions, India, China, and Brazil’s contribution to warming has risen by 110%, 56%, and 55%, respectively, with respect to carbon dioxide-related warming between 1851 and 2021.
- Emissions of CH4 and N2O are more ambiguous than emissions of fossil CO2, so any changes in the ranking of contributors due to the inclusion of CH4 and N2O should be viewed with caution.
References:
https://www.nature.com/articles/s41597-023-02041-1
https://pubmed.ncbi.nlm.nih.gov/33028999/
https://essd.copernicus.org/articles/14/4811/2022/
https://earthobservatory.nasa.gov/world-of-change/global-temperatures
