The following are a few general criticism on the paper.
(I did not read the entire paper so I am uncertain if all of these apply)
...when corrected for El Nino and volcanic activity, the satellite
record shows the same warming trend as the surface record.
...the sun's influence is less than one-fifth of the human-related
...changes in precipitation and temperature related to climate change
may have adverse effects (on soil moisture, disease and insect
infestations) that could negate any gains from CO2 fertilization.
The authority of the article is open to question as it has not
undergone peer review. Peer review is the process of evaluation
(usually anonymous) by technical specialists whereby most scholarly
journals judge the suitability of an article for publication.
OP-ED SCIENCE A MYTH: GLOBAL WARMING IS HAPPENING
THOMAS R. KARL, KEVIN TRENBERTH and JAMES HANSEN
...scientific evidence shows that greenhouse gases, such as carbon
dioxide, can remain in the atmosphere for centuries.
Most climate change detection studies find a strong likelihood, a 95%
chance, that the pattern and magnitude of global warming are related
to man-made causes.
Seven of the ten warmest years on record (since 1853, when
instrumental records begin) have all occurred in the past ten years.
Oregon Institute of Science and Medicine
Fakhri Bazzaz, a plant physiologist at Harvard, has found that carbon
dioxide-enriched air accelerates short-term plant growth, but his
studies were carried out under controlled greenhouse conditions and
are difficult to translate to a larger scale.
(Some recent info about climate change)
Scientific American Frontiers: "Hot Times in Alaska"