Original sentence: It is also unknown if this drift will continue to accelerate.The Earth's magnetic north pole is drifting from northern Canada towards Siberia with a presently accelerating rate — 10 km per year at the beginning of the 20th century, up to 40 km per year in 2003
Edited sentence: The Earth's magnetic north pole is drifting from northern Canada towards Siberia with a presently accelerating rate — 10 km per year at the beginning of the 20th century, up to 40 km per year in 2003, and since then has only accelerated