Do you understand the difference between the 'apparent' slope of a line on a 570 million year scale and one on a scale of 800,000 years?
Let's imagine two plots. Both cover, say, 1,000 ppm CO2 on the vertical scale but one's horizontal scale is 600 million years and the others is 1 million years. Both plots show a data trend making a 45 degree angle with the horizontal. What are the actual rates shown on both graphs.
Graph one changed 1,000 ppm in 600 million years. That is a rate of 1.667E-6 ppm/year. The other changed 1,000 ppm in 1 million years. It's rate is 1.0E-3. Versteht?