key: cord-0766178-gaargjn5
authors: Kumar, Abhinandan; Singh, Pardeep; Raizada, Pankaj; Hussain, Chaudhery Mustansar
title: Impact of COVID-19 on greenhouse gases emissions: A critical review
date: 2021-09-17
journal: Sci Total Environ
DOI: 10.1016/j.scitotenv.2021.150349
sha: 3f69b3e562c77333e75a18f10f923b7bd654f78b
doc_id: 766178
cord_uid: gaargjn5

The global outburst of coronavirus 2019 (COVID-19) has posed severe challenges to human health, environment, energy and economy all over the world. The stringent measures to control the spread of COVID-19 results a significant slowdown in economic activities which in turn affected the environment by reducing the greenhouse gas (GHG) emissions, specifically lower atmospheric CO2 levels. Considering that, the present study intends to highlight the substantial impact of COVID-19 pandemic on GHG emissions, by systematically reviewing the available scientific literatures. The study further outlined the variation in GHG emissions by comparing the data focused on pre-pandemic, during pandemic, and post-pandemic (predictions) scenarios. Further, the assessment on elevating CO2 levels, global economic, and energy impacts of COVID-19 has also been reviewed. Also, the possible recovery plan for the framework of sustainable environmental and energy development is presented. Finally, the review concludes with an insightful summary involving the challenges and future outlook towards sustainable development goals in a hope that the present study can help the researchers to assess the global environmental and energy related consequences.

With the global reliance of energy on fossil fuels, the environmental, social, and economic conditions worldwide are unstable. Burning of fossil fuels for the fulfillment of energy demands tend to release vast amounts of greenhouse gases (GHGs) like CO 2 , CH 4 , NO 2 etc. and causing egregious effects on climate. From observations, industrialization and use of fossil-fuel based automobiles are causing drastic upsurge in GHG emissions out of which transportations is responsible for one fifth of aggregate CO 2 emission with 75 % contribution from the road transport (Siddique et al., 2021) . However, with increasing population and energy demands all over the world, the chances of elevating CO 2 levels are most likely possible. Therefore, more stringent actions are required to control and limit the CO 2 emission into the atmosphere from transportations and other energy-related sectors. At the same time development of environmentally friendly and economic energy sources with the promise of cleaner environment in the future are highly desirable.

Notably, spread of the novel coronavirus has created unprecedented influence on the global energy consumption and GHG emissions due to the government enforced lockdown and virtual halt of chief economic activities (Smith et al., 2021) . During the initial shutdown period, the restrictions on international air transportations and industrializations substantially reduced the CO 2 emissions proved by various studies.

Typically, after analyzing the emissions data for six economic regions across 69 countries, total 17% of reduction in daily CO 2 emissions was observed by April 2020 in contrast with that only after understanding the long-term effects and gathering evidences in this regard will help to form firm environmental and energy related policies related to the post-COVID-19 economic recovery. However, there are certain chances that the reduced CO 2 levels in 2020 may only be temporary and the moment different countries begin to stabilize their economy, the situation might get worst. For instance, a report from 'The United States Energy Information Administration' has forecasted that the atmospheric CO 2 levels will upsurge by 6% in 2021 in order to recover the economy (IEA, 2011) by using excessive energy resources. So it is the high time for the governments to form strict policies and eliminate the use of fossil fuels and shift to a more sustainable and ecofriendly energy transition.

Till date, various review articles (Table 1) have critically investigated the impact of COVID-19 on various parameters involving environmental and energy concerns along with the global economy (Elavarasan and Pugazhendhi, 2020; Khan et al., 2021; Le et al., 2020; SanJuan-Reyes et al., 2021; Shakil et al., 2020) . However, an all-inclusive report which covers the latest information on impact of COVID-19 on greenhouse gas emission along with assessment on CO 2 emissions, global economy, energy influence, and sustainable policies for better future is still missing. In this context, the basic theme of this review is to outline the impact of COVID-19 pandemic on GHG emissions. The review critically highlights the energy consumption scenarios and the subsequent CO 2 emission levels pre-pandemic, during pandemic, and post-pandemic with special emphasis on assessment on elevating atmospheric CO 2 levels and global economic energy impact. The long term and short term impact of COVID-19 on environment and sustainability has also been comprehensively summarized. A critical discussion on the influence of COVID-19 on GDP along with the utilization of clean energy technologies for sustainable solutions of green economy has been presented. Finally, the review concludes with the important insights of the learning and proposes possible tactics as future recommendation for sustainable environment. We anticipate that this timely and up J o u r n a l P r e -p r o o f Journal Pre-proof to date study with substantial information can be helpful to amend the environmental policies and develop more sustainable solutions to fight against upcoming pandemics in the future. <Please insert Table 1 here> 

The present study was accomplished by collecting the short-time relevant published literature, case studies, and information from different government and non-government organizations related to environmental and energy consequences of COVID-19 pandemic.

Primary literatures from the major scientific flux were recorded using Scopus, Science Direct, and Google Scholar. It is worth mentioning that the abundance of data available in a particularly short time as can be seen in Figure 1 which depicts the number of publications in the respective years using Scopus database search with keywords "COVID-19 + Greenhouse gas emissions" and "COVID-19 + energy consumptions". After analyzing the available literatures, the present review article compiles and outlines the data and information with clear emphasis on impact of COVID-19 pandemic on environmental and energy issues, as argued in the forthcoming sections. (Rohde and Hausfather, 2020) . The report presented following key observations (Ritchie and Roser, 2020) :

 In contrast with ocean, the average temperatures over land have increased twice with an average increment by 1.32 ± 0.04 °C. While, the temperature of ocean surface across the world has increased by only 0.59 ± 0.06 °C.

 As can be seen from Figure 2b , the temperature change is not uniform throughout the globe. Typically, the regions near the poles with high latitudes sowed an upliftment in warming by 3-5 °C and are often the regions with high risks of permafrost, sea ice, and glacial melts.

A comprehensive report on global GHG and CO 2 emissions from PBL Netherlands Environmental Assessment Agency revealed that the year 2019 before the COVID-19 pandemic was the second warmest year with an average increase of +0.95 °C land and ocean surface temperatures in the 140 year record (Olivier and Peters, 2020) . This global increase in temperature was ascribed to the augmented GHG emissions all over the world. From Figure  emission and partially counterbalanced an increase in GHG emission mainly by China, India, and Russian Federation. The noteworthy increase in the emission rate was aided by the incremented combustion of fossil-fuels altogether by 0.9% in 2019 leading to the 12% enhancement in CO 2 and CH 4 emission along with 50% increased F-gas emission.

However, the global outbreak and spread of COVID-19 in 2019 not only drastically threatens human health, but also affected the global GHG emissions (Bai et al., 2020) . During the pandemic most the countries implemented stringent measures like lockdowns in order to control its spread. Such measures have had substantial effects on global economy, and consequently on emissions throughout the world. Of note, it was very difficult to observe the real time change in energy consumption and subsequent emission of GHG so most of the studies have utilized the proxy data on mobility from Google, Apple, and TomTom to analyze the emission trends during 2020 along with some real-time data which depicts activity levels like electricity production and consumption. Moreover, some of the studies estimated the impact of COVID-19 during 2020 using emissions data for year to date while others evaluated for the full year (Le Quéré et al., 2020; Liu et al., 2020c; Olhoff and Christensen, 2020) . The report further revealed that the GHG emissions were collectively declined by 7.1 % till 1 November 2020 globally due to the restrictions and subsequent variations in energy consumption. Furthermore, maximum of 17 % reduction in the emissions were recorded in April 2020 based on the emission data only which reduced to ~12 % in the mid-June due to partial upliftment of the restrictions in some of the countries. However, as per the 2020 full-year estimation data for CO 2 emissions, a total 7 % and 8 % decline was observed in contrast with the estimated data in 2019 by IEA 2020 and Enerdata 2020 reports, J o u r n a l P r e -p r o o f Journal Pre-proof respectively (Programme, 2020) . Thus, the restrictions in mobility to limit the transmission of COVID-19 substantially influence the emission levels globally.

For a fact, it is very difficult to predict the long-run effects of COVID-19 on GHG emissions throughout the world considering the rapid mutations in virus and how the extent of vaccination will bring the pandemic under control (Gautam and Hens, 2020) . However, it is being estimated that in the short run (by 2025), the COVID-19 and response measures would cause regional decline in the GHG emissions in almost all the countries (OECD, 2021). More interestingly, the GHG emissions and material use in India will also face large reductions in India owing to the influence of energy systems. On the other hand, by the year 2040, both reduced GHG emissions and economic losses will be partly faded away globally with some significant lessons from the pandemic. Particularly, the regions with Organization for Economic Co-operation and Development (OECD) will continue to outstrip gross domestic product (GDP) impacts with reduced emissions level due to specialized economies with clean sectors ascribed to the COVID-19 pandemic and response measures. To summarize, the real-time evaluation of the impacts of COVID-19 pandemic on GHG emissions is far from being possible with the current disaster of epic proportion and great complexity. fuels in petrochemical processes, carbon as reducing agent in metallurgical procedures, the fermentation of biomass, and thermal decomposition of dolomite and limestone in lime production or cement formation (Gale, 2004) . As reviewed earlier, the crises of COVID-19 pandemic and its global spread depicts an epoch-defining event with clear impacts on human health, economy, and environmental consequences like CO 2 emission and climate change (Barouki et al., 2021; OECD, 2021) . Notably, it was observed that in contrast with 2019, the initial months of 2020 were recorded to be warm across northern hemisphere, suggesting the significant role of COVID-19 restrictions posing disruption in economic activities and energy generation (Aletta et al., 2020; Hale and Leduc, 2020) . For better understanding of the relationship between variation in CO 2 emissions over the years by the changes in energy production, population, real GDP per capita, and carbon intensity Hale et al. What's more, owing to the increased global attention on environmental sustainability and the focus on inventing and utilizing more lower-emission technologies, emission levels seems to be stabilized since 2013 despite of non-stop economic advancement.

Also, it was observed that the overall cost accompanied carbon emissions and the subsequent climate change results about 5% decline in GDP each year which can be increased up to 20% if the necessary actions are not taken immediately (Stern and Stern, 2007) . Furthermore, to control CO 2 emission levels, the energy demand needs to be reduced which will definitely influence the GDP. Hence, the substantial attempts to control energy consumption in order to influence the CO 2 emissions will exert negative impact on economic J o u r n a l P r e -p r o o f growth as energy is the major constituent in the industrial processes (Acheampong, 2018) .

Consequently, these influential parameters and counter arguments result inconsistency in between energy, environmental conservation and economic policies.

With COVID-19 pandemic and the challenge to control the transmission, graphs of industrial production and energy consumption showed substantial decline (30%) in some countries owing to the strict lockdowns which partly affected the CO 2 emission levels (Economics, 2020; Liu et al., 2020b) . Despite of seasonal variations, there has been a significant reduction in the daily CO 2 levels as compared with 2019. From Figure 5 , an estimated trend depicting global decline of 7.8 % in the CO 2 emissions was observed during initial 4 months of 2020 (solid black line) in contrast with 2019Q1 represented via dashed black curves (Liu et al., 2020a) . Interestingly, in the first quarter of 2020, China showed highest -9.3% decline in emissions with progressively smaller reduction of -8.4 %, -4.7 %, -3.6 %, -2.5 %, and -2.1 % in Europe and United Kingdom, the United States, Japan, India, and Russia. However, the apparent reductions in CO 2 emissions were not similar in most of the countries and the greater decline was observed in April and March as compared to February due to the stringent restrictions in movement as shown in Table 2 . The data in Table   2 is obtained from a report published by Cornell University in General Economics (Liu et al., 2020a) . Table 2 (Smith et al., 2021) . The study presented global crosssectional and time interdependencies of the effect of COVID-19 on energy consequences and global propagation. After analyzing the data for thirty two countries responsible for 81 % of aggregate CO 2 emissions owing to the use of fossil-fuels, significantly negative consequence of COVID-19 on fossil-fuels consumption was recorded with limited CO 2 emissions from 2020Q1-2021Q4. However, in order to improve the economy due to the global pandemic, most of the countries may consume more energy than the pre-pandemic era and aid to the increased emission levels. Therefore, it can be anticipated that the pandemic and consequent shut-downs won't impact the emissions over a two-year time zone and the need to develop stringent climate-control policies should be taken more seriously.

COVID-19 pandemic has caused considerable effects on the global economy and energy sector (Eroğlu, 2021; Gettelman et al., 2021) . For a fact, COVID-19 has shocked our global economy and the damage is even worse than the World War II (Insights, 2020; Watts, 2020) . The safety measures involving travel restrictions, quarantine, and border shutdowns in J o u r n a l P r e -p r o o f Journal Pre-proof order to flatten the pandemic curve have caused justified uncertainties about looming longlasting economic crisis (Burkert and Loeb, 2020) . The COVID-19 induced economic loss is primarily caused by a significant decline in demand for many goods and services. As a result of global economic fallout, the fossil-fuel demand throughout the world will also be hindered drastically (Mohideen et al., 2021) . The observations from IEA global energy review in the year 2020 has showed 3.8 % reduction in the energy demand during January to March and predicted ~ 6 % decline at the end of 2020 which is nearly correct. Moreover, the economy related to fossil-fuels like oil, coal, and gas has showed a significant decrease by 5 %, 8%, and 2%, respectively (Review, 2020) . Of note, the researchers predict the fallout in economy would be greatly large than the global energy financial crisis occurred in 2008 (Mohideen et al., 2021) .

Economic crisis are usually resulted via a shock to demand or a shock to supply. But the pandemic disturbed both of the components all together leading to global economic crisis (Oncioiu et al., 2021) . The government imposed safety measures restricted the mass access to their professional activities which altered the production and eventually the cumulative supply of the economy. Furthermore, restrictions in the free moment caused limited consumption of goods and services rendered decline in aggregate demand and directly affected the economy as can be seen from Figure 6a . Also, the different set of variables affected by the global pandemic such as private consumption due to the household responses, government consumption owing to the safety measures to stabilize the economy, unemployment as a result of shutdowns and least possibilities of working from home, and the export as a result of movement restrictions are also summarized in Figure 6a . Typically, the private and government consumption has critically influenced the aggregate demand on the J o u r n a l P r e -p r o o f other hand, unemployment along with decline in export has also hindered the aggregate supply resulting into significant impact on economy globally.

In a fascinating study Smith et al. analyzed global fossil fuel consumption by using unique quarterly data of natural gas, coal, oil consumption, equity prices, exchange rates, and fossil-prices for 32 primary CO 2 emitting countries (Smith et al., 2021) . The report further estimated the forecast for coal, oil consumption, and natural gas with respect to three different scenarios by 8-quarter horizon variation in GDP for the developing economies ( Figure 6b ). Comparing Scenario 0 (GDP forecast published in January 2020 by IMF, prepandemic observations (IMF, 2020a)) with Scenario 1 (IMF forecast in April 2020, (IMF, 2020b)), the negative impact of COVID-19 on GDP due to economic shock in Asia (January-February) along with Europe and US (March-April) can be clearly seen. The results further estimated that the global economy might return to the difficult and long-run growth path around 2020Q4 without much hindrance from the second outbreak. Scenario 2 predicts the impact of second wave of COVID-19 on GDP growth rate around 2021Q1 and Q2 which showed a significant decline, slightly lower in magnitude than the one observed during first wave.

To sum-up, the economies of developing countries are highly energy-intensive and in order to improve the current scenario, more efficient and ecofriendly energy sources are highly desirable. The developed countries with stable economies should collaborate with developing countries having lower economy by enabling technical assistance along with planned investments to support market-based energy policy agenda. Also, the designed policy should be focus on investors and industrial organizations with a security of investment under difficult situations like pandemic.

The COVID-19 pandemic has caused unprecedented crisis all over the world and governments in different countries are strategizing stimulus plans for damage control and sustainable recovery. The task to ensure public health, economy, and climate change all together is challenging yet highly desirable. Sustainable speculation in public health is of highest concern along with a synergistic balance between economic recovery and climate issues (Gillingham et al., 2020; Siddique et al., 2021) . Notably, development of efficient energy resources can benefit remarkably by providing job opportunities, lowering the electricity bills and support economy, and enhance the energy use efficacy (Apostolos et al., 2013; Kumar and Zare, 2019) . Typically, projects to run efficient energy sources should involve replacement of inefficient electrical appliances throughout and upgrade the current electrical system with advanced ones to achieve maximum efficacy. The best example in this regard is the up-gradation of streetlights in India with LEDs rendering 5 million tons decline in GHG emissions in 9 years along with the creation of 13,000 jobs (Siddique et al., 2021) . A smooth transition to renewable energy technologies via bioenergy with carbon capture and storage along with atmospheric carbon capture can also be a fascinating strategy for moving towards energy efficiency (Budinis, 2020; Ope Olabiwonnu et al., 2021) . Other than this, hydrogen economy is another promising approach for low carbon energy system since hydrogen is a versatile carbon-free energy carrier and can support energy service across various energy sectors (Grigoriev et al., 2020; Thomas et al., 2020) . Considering this, so many developed countries have formed a policy framework along with certain national strategies to deploy hydrogen and fuel cell technologies as shown in Table 3 reprinted from Mohideen et al. (Mohideen et al., 2021) .

Addressing environmental and climate related crisis necessitates integrated scientific knowledge and engineering expertise to eliminate the negative impacts with sustainable technical solutions. However, chasing sustainable technological aspect involves societal, J o u r n a l P r e -p r o o f political, organizational, and economic endeavors with certain non-technical challenges (Geels, 2004) . The vision of 'green economy' started in 2015 when various countries adopted a 2030 agenda for sustainable development with the goals of tackling rising poverty and providing basic social needs along with improvement in environmental and climate change conditions (Söderholm, 2020) . Hence, the sustainable development objective also addresses the worldwide concerns related to environmental pollution and energy crisis by forming a synergistic relationship between ecological system and economy. In this regard, cleaner technological innovation is a promising means of reducing environmental pollution and climate change crisis by promoting the green growth (Popp, 2012) . For instance, various upper-middle and high income countries utilized advanced pollution reduction techniques to help improve the local air quality by decontamination of some pollutants (Dasgupta et al., 2002) . However, to employ such technologies often entails a considerable starting cost which makes the process a lot difficult. Therefore, the development of energy efficient technologies such as appliances, vehicles, and industrial tools promotes less environmental pollution.

Additionally, the implementation of stringent policies to flourish green technologies in the market should be a prior initiative towards sustainable development. Table 3 here> For a fact, extensive debate exists to operationalize sustainability across distinct contexts, however, strong sustainability refers to the ideal prescription for sustainability and human life and the exact meaning is still not clear (de Oliveira Neto et al., 2018) . COVID-19 pandemic has elicited global response via exposing so many flaws in the present policies and stimulated the governments to construct stronger sustainability agenda by focusing on the following points (Rume and Islam, 2020) ;

For sustainable industrialization, it is important to maintain an energy efficient environment by using cleaner fuels and technologies. Also, industrial waste J o u r n a l P r e -p r o o f management and emissions control policies should be strictly designed to avoid environmental hazards (Pan, 2016) .

To reduce the transport induced emission, it is highly desirable to encourage people about the use of public transport and switch to a vehicle sharing system for better environment (Rume and Islam, 2020) .

Cleaner and greener energy sources like solar, wind, hydropower, biomass, and geothermal heat can reduce the global reliance on fossil-fuels and help to decline the GHG emissions all over the world by simultaneously meeting the worldwide energy demands (Ellabban et al., 2014) .

The three R's (Reduce, Reuse, and Recycle) approach can be substantially important to lessen the burden of wastes and environmental pollution. Therefore, it is of great interest to reduce the use of raw materials and waste production along with the proper management of waste segregation and disposal issues (Hysa et al., 2020) .

Lastly, for a better and sustainable global environmental protection collective efforts are required with stringent policies and their proper implementation all over the world (Rume and Islam, 2020) .

The outburst of COVID-19 pandemic has jolted the world ecosystem and discloses various bottlenecks associated with the current policies to tackle such global crisis. The inability to safeguard human health, economy, and energy crisis all over the world created a serious awareness that it is the high time to amend policies and implement them strictly to recover the ecosystem and global economy synergistically. Thus, based on the availability of scientific data, efforts have been made to present an in-depth overview on impacts of COVID-19 on GHG emissions globally. It is highly anticipated that by assessing the emission J o u r n a l P r e -p r o o f levels pre-pandemic, during pandemic and post-pandemic predictions, an insight into the relationship between climate changes with COVID-19 spread can be offered. However, the real-time monitoring of climate change with the pandemic is still challenging owing to the lack of data for operational forecasting of weather, ecological, and hydrological system. J o u r n a l P r e -p r o o f the months February, March, and April in 2020 (Liu et al., 2020a) . 

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☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests

 Tables   Table. 1 Summary of different review articles published on impacts of COVID-19 on environment, energy and economy. (Le et al., 2020) J o u r n a l P r e -p r o o f