It is reported that due to a large number of greenhouse gases emitted by human beings, global temperature has continued to rise over the past 150 years. However, compared with 1970 to 1998, the rate of increase in global average surface temperature has slowed significantly since the past 15 years. The rise in temperature is not significant, so global warming is not so severe. If the following are true, what will most weaken the above argument? ['Ocean and climate system adjustment processes allow ocean surface heat to be transported to the deep ocean.', 'This phenomenon occurred in the 1950s and 1970s, and then began to accelerate warming.', 'UN climate experts point out that carbon dioxide concentration in the air is at its highest point in 800,000 years.', 'Many natural disasters caused by climate warming in recent years.']