Being aware that CO2 was a greenhouse gas, in 1977 Budyko agreed that adding CO2 emissions to the atmosphere would be expected to warm the climate. Budyko realised that warming due to increased CO2 might provide more favourable conditions for the plant growth needed to feed the growing human population. By 1979, interest in the CO2 question was beginning to move into the international arena. The slow carbon cycle determines the abundance of CO2 in the Earth's air and oceans on time scales of tens to hundreds of millions of years and is controlled by tectonics, volcanism and weathering. To reduce uncertainties about global ocean dynamics and the rates of ventilation and mixing in the deep ocean, and to improve understanding of the role of the ocean in the global climate system, the World Climate Research Programme launched a major international global experiment, the World Ocean Circulation Experiment (WOCE).