Methane

Nitrous

CO2

Greenhouse

Levin, Lin and Chu [25]

0.3278

0.1587

−3.989*

−2.0174*

Harris and Tzavalis [20]

0.9718

0.933

0.9468

0.9383

Breitung [21]

2.6478

−0.0376

2.6297

2.8004

Im, Pesaran and Shin [22]

−1.0118

0.5619

−1.7418*

−1.5236

Maddala and Wu [19]

48.1682

54.5412

69.0915

51.1836

Choi [24]

43.6091

74.2681*

101.79*

82.7779*

Hadri [23]

87.0710

103.349

121.916

99.4581

Pesaran t-bar [13]

−1.0630

−1.8640

−1.7940

−1.5460