Authors	Country	Period	Methodology	Findings
Afriyie et al. (2023)	37 African countries	1995-2017	PMG	URB has no significant effect on CO₂
Aladejare (2023)	29 African countries	1970-2019	CS-ARDL	URB increases EF
Abid (2023)	Saudi Arabia	1990-2015	QR	URB increases CO₂
Huang et al. (2023)	ASEAN countries	1995-2018	CS-ARDL, AMG, CCEMG	URB increases GHG
Khan and Majeed (2023)	Pakistan	1980-2018	OLS	URB increases CO₂
Kwakwa et al. (2023)	Ghana	1971-2018	ARDL	URB decreases CO₂
Liu et al. (2023)	China	1995-2020	PMG	URB has no significant effect on CO₂
Opuala et al. (2023)	West Africa	1980-2017	PMG, AMG	URB increases EF
Otim et al. (2023)	Kenya	1971-2014	ARDL	URB decreases CO₂
Raza et al. (2023)	Bangladesh	1980-2020	ARDL	URB increases CO₂
Sofuoğlu et al. (2023)	Türkiye	1970-2020	FARDL	URB increases CO₂
Voumik et al. (2023)	5 Asian countries	1972-2021	CS-ARDL, AMG, MG, CCEMG	URB increases CO₂
Wang et al. (2023)	China	1970-2021	ARDL	URB increases CO₂
Warsame et al. (2023)	Somalia	1985-2016	ARDL, KRLS	URB increases CO₂
Zhang et al. (2023)	10 nations	1990-2019	PMG	URB increases CO₂
Aladejare (2022)	5 African countries	1990-2019	FE, RE, FGLS, AGM	URB decreases CO₂
Alvarado et al. (2022)	95 countries	1990-2018	AMG, CCEMG, DCCE	URB increases EF
Azam et al. (2022)	7 Asian countries	1990-2018	CS-ARDL, PMG	URB increases CO₂
Baajike et al. (2022)	16 West African countries	2005-2018	GMM, OLS, FE, RE	URB increases CO₂
Chen et al. (2022)	China	1998-2019	FE, RE	URB reduces NDVI
Dada et al. (2022)	Nigeria	1970-2017	ARDL	URB decreases EF
Ehigiamusoe et al. (2022)	31 African countries	1990-2019	FMOLS, PMG, AMG	URB has an inverted U-shaped impact on CO2 and a U-shaped impact on EF
Hussain et al. (2022)	54 African Union countries	1996-2019	QR, FMOLS	URB increases CO₂
Li et al. (2022)	16 West African countries	1990-2018	AMG, CCEMG	URB increases CO₂
Jóźwik et al. (2022)	28 EU countries	2000-2018	FMOLS, MG, CCEMG, AMG	URB mitigates CO₂
Kahouli et al. (2022)	Saudi Arabia	1971-2019	ARDL	URB causes CO₂
Mignamissi and Djeufack (2022)	48 African countries	1980-2016	QR	URB increases CO₂
Sahoo and Sethi (2022)	NICs	1990-2017	MG, PMG, AMG, CCEMG	URB increases EF
Voumik and Sultana (2022)	BRICS	1972-2021	CS-ARDL	URB increases CO₂
Wang et al. (2022)	156 countries		Threshold regression	URB increases CO₂ and EF
Yang and Khan (2022)	30 nations	1992-2016	AMG, CCE	URB increases EF
Adebayo et al. (2021)	Latin America	1980-2017	FMOLS, DOLS	URB increases CO₂
Dimnwobi et al. (2021)	5 African countries	1990-2019	CS-ARDL	URB has no significant effect on EF
Erdogan et al. (2021)	23 African countries	1960-2016	CUP-FM, CUP-BC	URB increases EF
Iheonu et al. (2021)	34 African countries	1990-2016	QR	URB increases CO₂
Islam et al. (2021)	Bangladesh	1972-2016	ARDL	URB increases CO₂
Liu et al. (2021)	5 Asian countries	1995-2014	DOLS, FMOLS	URB increases CO₂
Majeed et al. (2021)	GCC	1990-2018	CS-ARDL	URB increases CO₂
Musah et al. (2021)	16 West African countries	1990-2018	Driscoll-Kraay regression	URB increases CO₂
Nathaniel (2021)	Indonesia	1971-2014	ARDL	URB increases EF
Nathaniel et al. (2021b)	Latin American and Caribbean countries	1990-2017	AMG, CCEMG	URB increases CO₂
Nathaniel et al. (2021a)	10 countries	1995-2016	CUP-FM, CUP-BC	URB reduces EF
Nurgazina et al. (2021)	Malaysia	1978-2018	ARDL	URB increases CO₂
Onifade et al. (2021)	E7 economies	1990-2016	AMG, FMOLS, DOLS	URB increases CO₂ and EF
Qayyum et al. (2021)	5 Asian countries	1991-2017	ARDL	URB increases EF, but it moderates the impact of informal economy on EF
Rafiq et al. (2016)	22 countries	1980-2010	MG, DOLS, FMOLS	URB has insignificant impact on CO₂
Raghutla and Chittedi (2021)	BRICS	1998-2016	FMOLS	URB reduces CO₂
Rahman and Alam (2021)	Bangladesh	1973-2014	ARDL	URB increases CO₂
Villanthenkodath et al. (2021)	India	1971-2014	ARDL	URB reduces CO₂
Yameogo (2021)	Burkina Faso	1980-2017	ARDL	URB increases DF
Younis et al. (2021)	BRICS	1993-2018	GMM	URB increases CO₂
Zhou et al. (2022)	Pakistan	1980-2018	ARDL	URB decreases EF
Abbasi et al. (2020)	8 Asian countries	1982-2017	FMOLS	URB increases CO₂
Adams et al. (2020)	19 African countries	1980-2011	IV-GMM	URB decreases CO₂
Adedoyin and Bekun (2020)	6 island countries	1995-2014	FMOLS, PMG	URB reduces CO₂
Adedoyin et al. (2020)	12 African countries	1980-2014	PMG	URB increases CO₂
Ahmed et al. (2020b)	G7 countries	1971-2014	CUP-FM, CUP-BC	URB increases EF
Ahmed et al. (2020a)	China	1970-2016	ARDL	URB increases EF
Akorede and Afroz (2020)	Nigeria	1970-2017	ARDL	URB reduces CO₂
Amin et al. (2020)	13 Asian countries	1985-2019	FMOLS	URB mitigates CO₂
Anser et al. (2020)	SAARC	1994-2013	FE	URB has a U-shaped impact on CO₂
Anwar et al. (2020)	9 Asian countries	1980-2017	FE	URB increases CO₂
Asongu et al. (2020)	African countries	1980-2014	PMG	URB increases CO₂
Danish et al. (2020)	BRICS	1992-2016	FMOLS, DOLS	URB decreases EF
Langnel and Amegavi (2020)	Ghana	1971-2016	ARDL	URB increases EF
Mosikari and Eita (2020)	African countries	2005-2019	PSTR	URB reduces CO₂
Muhammad et al. (2020)	65 countries	2000-2016	QR, 2TLS	URB has an inverted U-shaped impact on CO₂
Nathaniel (2020)	Nigeria	1980-2016	ARDL	URB increases CO₂
Nathaniel and Khan (2020)	6 ASEAN	1990-2016	AMG	URB has no significant effect on EF
Nathaniel et al. (2020a)	MENA countries	1990-2016	AMG	URB increases CO₂
Nathaniel et al. (2020b)	6 countries	1990-2014	AMG	URB increases EF
Nosheen et al. (2020)	11 Asian countries	1995-2018	FMOLS, DOLS	URB increases CO₂
Rahman and Vu (2020)	Australia and Canada	1960-2015	ARDL	URB increases CO₂
Shehu (2020)	Nigeria	1974-2015	ARDL	URB reduces CO₂
Yu (2020)	China	2003-2017	Dynamic spatial panel	URB reduces CO₂
Acheampong (2019)	46 African countries	2000-2015	GMM	URB increases CO₂
Adams and Nsiah (2019)	28 African countries	1980-2014	FOLS, GMM	URB mitigates CO₂
Ali et al. (2019)	Pakistan	1972-2014	ARDL	URB triggers CO₂
Baloch et al. (2019)	59 countries	1990-2016	Driscoll-Kraay regression	URB increases EF
Danish and Wang (2019)	11 countries	1971-2014	CCEMG	URB increases EF
Dogan et al. (2019)	4 countries	1971-2013	ARDL	URB increases EF
Gasimli et al. (2019)	Sri Lanka	1978-2014	ARDL, FMOLS	URB reduces CO₂
Khan et al. (2019)	Pakistan	1971-2016	ARDL	URB reduces CO₂
Khoshnevis and Dariani (2019)	18 Asian countries	1980-2014	PMG	URB increases CO₂
Nathaniel et al. (2019)	South Africa	1965-2014	ARDL, FMOLS, DOLS, CCR	URB mitigates EF
Li and Zhou (2019)	China	1996-2015	FMOLS	URB increases CO₂
Lv and Xu (2019)	55 middle-income countries	1992-2012	PMG	URB reduces CO₂
Phong (2019)	ASEAN-5	1971-2014	FE, RE	URB increases CO₂
Ponce and Alvarado (2019)	100 countries	1980-2017	DOLS	URB increases CO₂
Salahuddin et al. (2019a)	44 African countries	1984-2016	MG, PMG, CCEMG, AMG	URB increases CO₂
Salahuddin et al. (2019b)	South Africa	1980-2017	ARDL	URB increases CO₂
Salim et al. (2019)	13 Asian countries	1980-2010	MG, PMG, AMG	URB has no significant effect on CO₂
Wang and Dong (2019)	14 African countries	1990-2014	AMG	URB increases EF
Adams and Klobodu (2018)	26 African countries	1985-2011	GMM	URB increases CO₂
Effiong (2018)	49 African countries	1990-2010	FE	URB reduces CO₂
Hanif (2018)	34 African countries	1995-2015	GMM	URB increases CO₂
Kwakwa and Alhassan (2018)	Ghana	1971-2013	FMOLS	URB increases CO₂
Liu and Bae (2018)	China	1970-2015	ARDL	URB increases CO₂
Pata (2018)	Türkiye	1974-2014	ARDL, FMOLS	URB triggers CO₂
Phong et al. (2018)	Vietnam	1985-2015	ARDL	URB has no significant effect on CO₂
Raggad (2018)	Saudi Arabia	1971-2014	ARDL	URB reduces CO₂
Ali et al. (2017)	Singapore	1970-2015	ARDL	URB mitigates CO₂
Asumadu-Sarkodie and Owusu (2017)	Senegal	1980-2011	NIPALS	URB decreases CO₂
Charfeddine (2017)	Qatar	1970-2015	MS	URB increases EF
Charfeddine and Mrabet (2017)	15 MENA countries	1975-2007	DOLS, FMOLS	URB reduces EF
Behera and Dash (2017)	17 Asian nations	1980-2012	DOLS, FMOLS	URB has insignificant impact on CO₂
Bekhet and Othman (2017)	Malaysia	1971-2015	ARDL	URB has an inverted U-shaped impact on CO₂
Saidi and Mbarek (2017)	19 emerging nations	1990-2013	GMM	URB reduces CO₂
Zhang et al. (2017)	141 countries	1961-2011	FE	URB has an inverted U-shaped impact on CO₂
Adusah-Poku (2016)	45 African countries	1990-2010	PMG	URB increases CO₂
Ali et al. (2016)	Nigeria	1971-2011	ARDL	URB has no significant effect on CO₂
Azam and Khan (2016)	India, Bangladesh, Sri Lanka, and Pakistan	1982-2013	OLS	URB decreases CO₂ in Bangladesh and India, UBR increases CO₂ in Sri Lanka. URB has no significant effect on CO₂ in Pakistan
Destek et al. (2016)	10 European countries	1991-2011	DOLS, FMOLS	URB reduces CO₂
Dogan and Turkekul (2016)	USA	1960-2010	ARDL	URB increases CO₂
Li et al. (2016)	28 Chinese provinces	1996-2012	GMM, MG, PMG, DFE	URB increases CO₂, waste water, and waste solid
Lin et al. (2016)	5 African countries		FMOLS	URB reduces CO₂
Shahbaz et al. (2016)	Malaysia	1997-2011	ARDL	URB has a U-shaped impact on CO₂
Sheng and Guo (2016)	China	1995-2011	MG, PMG, DFE	URB increases CO₂
Siddique et al. (2016)	5 Asian countries	1983-2013	OLS	URB increases CO₂
Wang et al. (2016a)	ASEAN	1980-2009	FMOLS	URB increases CO₂
Wang et al. (2016b)	BRICS	1985-2014	FMOLS	URB increases CO₂
Cao et al. (2016)	China	1979-2013	TR	URB increases CO₂
Al-Mulali and Ozturk (2015)	14 MENA nations	1996-2012	FMOLS	URB increases EF
Al-Mulali et al. (2015b)	93 countries	1980-2008	FE, GMM	URB aggravates EF
Al-Mulali et al. (2015a)	129 countries	1980-2011	DOLS	URB increases CO₂ in lower-middle, upper-middle and high-income countries while no effect in low-income countries.
Asane-Otoo (2015)	45 African countries	1980-2009		URB has no significant effect on CO₂
Çetin and Ecevit (2015)	19 African countries	1985-2010	VAR	URB increases CO₂
Keho (2015)	Cote d’Ivoire	1970-2010	ARDL	URB reduces CO₂
Li and Lin (2015)	73 countries	1971-2010	FE, RE	URB reduces CO₂ in middle-/high-income nations, and increases CO₂ in low-income, middle-/low-income and high-income nations
Wang et al. (2015)	OECD	1960-2010	FE	URB has an inverted U-shaped impact on CO₂
Xu and Lin (2015)	30 China 30 provinces	1990-2011	Nonparametric additive regression	URB has an inverted U-shaped impact on CO₂ in eastern region, a positive U-shaped effect in central region, and insignificant nexus in western region
Onoja et al. (2014)	Africa	1960-2010	ARDL	URB has no significant effect on CO₂
Sadorsky (2014)	16 countries	1971-2009	MG, AMG, CCEMG	URB has no significant effect on CO₂
Shahbaz et al. (2014)	United Arab Emirates	1975-2011	ARDL	URB increases CO₂
Al-Mulali et al. (2013)	MENA	1980-2009	DOLS	URB triggers CO₂