The investigation explores the influence of economic growth, energy consumption, ICT, military expenditure, and tourism on CO2 emissions in the case of G20 countries. For consistency, the association between the explanatory variables and CO2 emissions is discussed individually in the following sections. The prior studies about the linkage among the intended variables deliberated and begin with economic growth and carbon emission by illustrating the current literature.
Economic growth and Carbon Emissions
The way through which economic growth influences carbon emissions is a controversial issue. The researcher involves in the debate with their decision about the link between economic growth on carbon emissions. The empirical analysis of Lau, Choong, & Eng (2014) employed data from 1984 to 2008 on Malaysia and claimed that economic growth stimulates carbon emissions positively which is statistically significant. The study of Ehigiamusoe (2020a) on 25 African countries by using data from 1980 to 2016 with the FMOLS approach represented that the real GDP has a positive and significant impact on CO2 emission. Ehigiamusoe & Lean (2019) analyzed the panel data of heterogeneous income groups of around 122 counties over the period of 1990–2014 with various estimation approaches, where the outcomes of DOLS showed that economic growth hastens the CO2 emissions in case of low and middle-income countries. However, for high-income countries, economic growth has a negative impact on CO2 emissions. Another investigation by Ehigiamusoe, Lean, Babalola, & Poon (2022) reported that CO2 emission is accelerated by GDP and that is statistically significant where the investigation was conducted on 31 African nations for the 1990–2019 period. The exploration of Aye & Edoja (2017) indicated that economic growth associated with carbon emission negatively in a lower progressive area, conversely, in the case of the higher progressive area it stimulates carbon emission positively and the results do not agree with the Environmental Kuznets Curve (EKC) hypothesis. The assessment was carried out with a panel of 31 developing countries. The experiment was accompanied by Magazzino (2016) employing the VAR model with data from 1971 to 2006 about 10 Middle East countries, to identify the inter-association among carbon emission, energy consumption, and economic growth. The outcomes of the experiment indicate that the economic growth of GCC countries affects carbon emissions negatively.
Energy Consumptions and Carbon Emissions
Most of the analysis about the interconnections between carbon emission and energy consumption emphasis total energy. Numerous factors affect energy consumption, but the concerning matter is how the environment is influenced by energy consumption. The development of a nation depends on the nation's ability to utilize energy resources efficiently. The researchers scrutinize the link of how energy consumption is related to carbon emissions, and the findings of their analysis varied from country to country and regime to regime. The analysis of Begum, Sohag, Abdullah, & Jaafar (2015) constructs a dynamic connection between carbon emission and energy consumption with the rejection of the EKC hypothesis in the case of Malaysia from 1970 to 1980. The findings specify that in the long run energy consumption is positively influences carbon emission. The study of Ehigiamusoe & Lean (2019) on heterogeneous income groups with different methods finds that energy consumption increases the CO2 emissions for low, middle, and high-income countries. Another investigation of EHIGIAMUSOE (2020b) on ASEAN + China with PMG estimation stated that energy consumption aggravates environmental degradation. In the case of African countries Ehigiamusoe et al. (2022) claimed that energy use intensifies the CO2 emissions, where the outcomes revealed from panel data of 1990–2019 by FMOLS approaches. According to the valuation of Waheed, Chang, Sarwar, & Chen (2018) using the ARDL model with annual data from 1990 to 2014 about Pakistan shows that the association between carbon emission and renewable energy consumption is negative and it is also claimed that carbon emission is reduced with the increase of renewable energy consumption. The study of Acheampong (2018) applies panel VAR and system GMM model to scrutinize the causal association among carbon emission, energy consumption, and economic growth of around 116 countries with data for 1990 to 2014. The outcomes describe mixed indications that; their association varies from regime to regime. Another investigation by Anwar, Sarwar, Amin, & Arshed (2019) examines 59 countries of different income groups for various factors by utilizing data from 1982 to 2015. The results designated that carbon emission and nuclear energy consumption have a bidirectional causality. Munir & Khan (2014) Argued that energy consumption affects carbon emission negatively and they find the outcome by applying the VEC model and Johansen Co-integration approach with data from 1980 to 2010 for Pakistan. According to Akin (2014; Esso & Keho (2016); Wang, Li, & Fang (2018), energy consumption negatively impacts carbon emissions amongst the various groups of countries with different income levels.
ICT and Carbon Emissions
Environmental quality and (ICT) information and communication technology is another hot issue of debate in the modern age. Modern innovations and technological progress are becoming a very concerning matter for climate change all over the world. In the present world, developed countries are innovating technology to save energy, including smart and green cities, updated industrial processes, and advanced and smart transportation systems. CO2 emissions are expected to alleviate with these developments (Lennerfors, Fors, & van Rooijen, 2015). The analysis of Higón, Gholami, & Shirazi (2017), with the panel of 142 economics by using data from 1995 to 2010, confirms that initially, ICT deteriorates the environmental quality, but after a specific time, updated ICT has contributed to decreasing and controlling of emission of CO2. The study of Batool et al. (2019) examines the link among carbon emission, ICT, economic growth, and energy consumptions for South Korea with data from 1973 to 2016. The results of the study designated that in the long run ICT diminishes environmental degradation. The study of Al-Mulali, Sheau-Ting, & Ozturk (2015) explored the heterogeneous connection for developing and developed countries amongst CO2 emission and internet retailing. The outcomes of the study claimed that CO2 emission is negatively influenced by internet users in developed countries, however, CO2 emission has an insignificant effect on internet retailing in the case of developing countries. Due to the slower speed of the internet in developing counties, there is a heterogonous effect. The empirical investigations of Santra (2017) about the BRICS countries indicated that technological innovation positively impacts carbon emissions. Another empirical study by Raheem, Tiwari, & Balsalobre-Lorente, (2020) explores the connection between CO2 emission and ICT in G7 countries and specifies that in the long run, CO2 emission is positively influenced by ICT. According to the investigations of Mensah et al. (2018), on OECD countries, of Santra (2017), on BRICS countries, of Shahbaz, Nasir, & Roubaud (2018), on France, of Jin, Duan, Shi, & Ju (2017), on China, of Dinda, (2018) on the US specified that to diminish carbon emission, technological innovations play a significant role. Identically, lots of advanced methods are innovated for the efficient utilization of energy. These modernized methods of using energy are friendly to the ecological system and environment in every country, and these approaches assist in reducing emissions of greenhouse gas.
Military Expenditure and Carbon Emissions
Environmental quality is affected by numerous factors. Recently, the researcher concentrated on military expenditure as one of the leading elements in the existing arms-dominated world. And one of the main focuses of modern technological innovations on military improvement. At present international military race is increasing day by day all over the world. The exploitation of various destructive tests and manufacture of military weapons generates many damaging elements that harm the environment's quality. In response to the issue, scholars investigate the association between military expenditures and the environment. The investigations of M. Bildirici (2017) assess the link between carbon emission and military expenditure for G7 countries by utilizing data from 1985 to2015 with the help of ARDL methods. The outcomes of the investigation indicated that carbon emission is positively influenced by the military expenditure of G7 countries, however causal analysis of the investigation shows that a unidirectional causal association between military spending and CO2 emission of G7 countries. Another investigation of M. E. Bildirici (2017) examines the long-run affiliation between environmental degradation and militarization by utilizing data from 1960 to 2013with the ARDL bond testing method. The results of the investigation indicated that carbon emissions are influenced by military spending positively in the case of the United States. It is considered that military expenditure is related to the activity of human beings and the movements of military personnel, extensive military equipment, & heavy-weighted military assets worldwide done by the sea, land, and air transportations. And those activities are responsible for a massive amount of pollution. And military campaigns need to consume enormous fuel in military ships, planes, and tanks (Jorgenson, Clark, & Kentor, 2010). According to the analysis of Ozcan & Apergis (2018), technological innovations created by states, militaries may be connected with declining emission methods. ICT industry developed by the innovations in the military sector. The analysis of (Bildirici, 2018) assesses the long-run association between CO2 emission and military expenditure by employing FMOLS and DOLS approaches with data from 1985 to 2015 for G7 countries. The findings of the analysis claimed that military spending and carbon emission has significant and positive associations.
Tourism and Carbon Emissions
Nowadays, tourism is becoming an identical factor for any economy all over the world. Tourism involves a country's infrastructural services, transportation services, and conditions of the resorts and restaurants for all of those required colossal energy consumption. And researchers and policymakers from around the world became worried about the potential link between tourism and the environment. According to the investigation of Miller, Rathouse, Scarles, Holmes, & Tribe (2010), it is difficult to make a sustainable tourism industry in the absence of awareness of tourists about the environment in the UK. Peeters & Dubois (2010), found that almost 4.4% of the world's carbon emissions are contributed by tourism, and most of these come from transportation. According to the exploration of Katircioglu (2014), carbon emission and tourism have a long-run association where environmental degradation refers to a proxy for Turkey. The investigation of Scott, Peeters, & Gössling (2010) reported that tourism has become a potential threat to the environment and it has badly influence on CO2 emission. The author also forecasted that in the coming days' tourism would be one of the most noticeable causes of carbon emission globally. Ehigiamusoe (2020c) indicated that environmental degradation is positively influenced by the tourism in case of African countries, where the study analyzed data from 1995–2016 with FMOLS methods. Another investigation by Dubois, Peeters, Ceron, & Gössling (2011) argued that tourism sectors could reduce carbon emissions, the consequences of alleviating global movement initiated by tourism by 2050. The authors also claimed that if we make a significant variation in the travel system, there is a possibility of diminishing carbon emissions in circumstances where the transportation system and tourism industry are connected to tourism which is essential to decrease emissions. Stefănica & Butnaru (2015), claimed that the tourism sector depends on environmental excellence, and tourism is affected by environmental factors like climate change, global warming, pollution, etc. Chen, Thapa, & Yan, (2018), Analyze the association among carbon emission, tourism, and economic growth in China from 2001 to 2015. The authors claimed that improvement in the tourism industry positively impacts CO2 emissions, and it is considered that transportations sectors are responsible for carbon emissions. The study of Paramati, Shahbaz, & Alam (2017), with panel data about the European Union, reported that the rise of the tourism industry could reduce carbon emissions.
However, the investigations of the recent studies indicate that there is no identical result about the association between CO2 emissions, economic growth, energy consumption, (ICT) information and communication technology, military expenditure, and tourism. Some of the investigations argued there are different shapes of their link. And some of them claimed that the connection between the dependent variable carbon emission and intended independent variables is positive, while other investigations contended that there is a negative relationship. And there are very few numbers of study which tries to investigate the effect of military expenditure and tourism on carbon emission. On the other hand, no previous research employed economic growth, energy consumption, ICT, military expenditure, tourism, and carbon emission simultaneously to investigate the interrelation among these variables. So, this empirical study tries to find reliable and consistent outcomes about the association among the intended variables.