Table 3.

Comparison of actual and predicted values of CO₂ emissions in China

Year	Actual value of CO2 emissions in China (million tons)	BP neural network			OLS
		Predicted value	Relative error (%)	Predicted value			Relative error (%)
1990	2088.854	2266.574	8.51		2216.484	6.11
1991	2200.885	2244.943	2.00		2250.705	2.26
1992	2295.775	2310.92	0.66		2240.567	2.40
1993	2500.73	2427.965	2.91		2351.068	5.98
1994	2599.503	2568.828	1.18		2533.655	2.53
1995	2900.265	2751.662	5.12		2833.114	2.32
1996	2871.981	2862.086	0.34		2916.22	1.54
1997	2925.749	2885.301	1.38		2932.003	0.21
1998	3020.717	2934.798	2.84		2933.306	2.89
1999	2920.897	2996.74	2.60		2888.392	1.11
2000	3099.685	3155.233	1.79		3231.622	4.26
2001	3255.951	3320.678	1.99		3335.584	2.45
2002	3511.728	3518.075	0.18		3515.335	0.10
2003	4068.095	4014.692	1.31		3925.766	3.50
2004	4741.831	4673.658	1.44		4731.485	0.22
2005	5407.518	5334.347	1.35		5518.728	2.06
2006	5961.808	5935.961	0.43		6050.772	1.49
2007	6473.211	6634.821	2.50		6621.774	2.30
2008	6669.112	6932.983	3.96		6804.283	2.03
2009	7131.512	7236.915	1.48		7105.661	0.36
2010	7830.969	7904.091	0.93		7844.707	0.18
2011	8569.653	8452.455	1.37		8346.275	2.61
2012	8818.413	8650.408	1.91		8658.672	1.81
2013	9188.381	8886.471	3.29		8905.344	3.08
2014	9116.341	9031.354	0.93		9110.081	0.07
2015	9093.304	9102.761	0.10		9186.184	1.02
2016	9054.476	9175.979	1.34		9269.595	2.38
2017	9245.582	9371.353	1.36		9353.227	1.16
2018	9528.214	9568.146	0.42		9525.992	0.02
2019	9809.198	9717.827	0.93		9763.737	0.46
MAPE (%)			1.89			1.96
MAE			90.41			90.43
MSE			13,030.95			13,116.35
RMSE			114.15			114.53