The cause of the 1998 spike is unresolved, but scientists are currently attributing it to a combination of increased wetland and rice field emissions as well as an increased amount of biomass burning.
A causa do pico de 1998 non está aclarada, pero os científicos atribúena a unha combinación do incremento das emisións en zonas húmidas e campos de arroz e a un aumento da cantidade de biomasa queimada.