ScienceNOW: Tropical Cyclones Turn Up the Heat

[bystander]

Tropical Cyclones Turn Up the Heat
Science NOW - 2010 Feb 24

Batten down the hatches! Researchers attempting to recreate a worldwide hot spell that began about 5 million years ago have found that such warm periods spawn more frequent hurricane-sized storms, which in turn can increase global temperatures and help prolong the warming by thousands or even millions of years. The findings could help scientists better understand our current climate and build new models to predict future trends.

The early Pliocene period, which began about 5 million years ago, made present-day global climate seem positively chilly. Although atmospheric carbon dioxide concentrations similar to today—350 to 400 parts per million then versus 387 ppm now—temperatures were as much as 4˚C warmer. Today, the phenomenon known as El Niño periodically spawns a zone of very warm water stretching across the mid-Pacific Ocean and causes a jump in severe weather patterns, particularly in North America. But back in the Pliocene, El Niño eventually settled in to become a more or less constant phenomenon, perpetuating the lousy weather.

Nature: doi:10.1038/nature08831

[bystander]

More tropical cyclones in past could play role in warmer future
PhysOrg Earth Sciences - 2010 Feb 24

More frequent tropical cyclones in Earth's ancient past contributed to persistent El Nino-like conditions, according to a team of climate scientists led by Yale University. Their findings, which appear in the Feb. 25 issue of the journal Nature, could have implications for the planet's future as global temperatures continue to rise due to climate change.

http://opa.yale.edu/news/article.aspx?id=7316

[BMAONE23]

But it seems that the increasing ocean temperatures actually has no direct correlation to a proposed increase in Hurricane frequency or strength

The World Meteorological Organization (WMO) issued a stunning statement in a recent report. Roger Pielke Jr. has the details on his blog.

http://wattsupwiththat.com/2010/02/24/w ... lone-data/

[bystander]

I think you missed the point. They aren't saying a warming climate causes more frequent or stronger hurricanes. They are saying the hurricanes are a contributing factor in the climatic changes.

"Changes in the frequency and distribution of these storms could be a significant component of future climate conditions."

[Chris Peterson]

But it seems that the increasing ocean temperatures actually has no direct correlation to a proposed increase in Hurricane frequency or strength

Apparently not so. A new report just published in Science makes a strong case for a decrease in hurricane frequency along with an increase in hurricane strength. The authors point out that given the very large natural variability in both these values, any past correlation between global warming and hurricane behavior would likely be lost in the noise. For the effect to become apparent will require additional warming and long observation periods.

[BMAONE23]

This graph shows the strength of hurricanes during the peak northern hemisphere season


Above: Hurricane ACE data from Ryan Maue. Note where 2009 is in the scheme of things.

You can see that, even though the temperature averages are climbing, net hurricane strength
has dramatically decreased and is at it's second lowest level since the low of 1977
There is however a discernable 11 year cyclical pattern that does tend to correlate to solar activity
though even toe '98 el nino didn't directly affect hurricane strangth.

http://wattsupwiththat.com/2010/02/16/r ... uestioned/

More trouble looms for the IPCC. The body may need to revise statements made in its Fourth Assessment Report on hurricanes and global warming. A statistical analysis of the raw data shows that the claims that global hurricane activity has increased cannot be supported.

Their source
http://wattsupwiththat.com/2010/02/16/r ... uestioned/

[Chris Peterson]

This graph shows the strength of hurricanes during the peak northern hemisphere season

Similar data is discussed in the Bender et. al. paper I referenced. As noted, their conclusion is that the observed hurricane pattern is probably not more than 20% influenced by anthropogenic inputs for the present sea surface temperatures, which makes it difficult or impossible to distinguish from the large natural variations. Their paper is a projection of future activity assuming continued increases in sea surface temperature.

(Personally, I completely avoid wattsupwiththat.com as a pseudoscience site. I don't think links to it belong on any forum advocating proper science.)

[bystander]

Hurricanes' effects on ocean temperature revisited
PhysOrg Earth Sciences - 2010 March 04

The role of hurricanes in the global climate system has gained interest ever since scientists suggested that strong hurricanes have become more frequent in recent decades and might continue to do so as the planet warms. Because hurricanes are known to influence the oceans and overall climate system, the consequences of the increase in the frequency of hurricanes could reach further.
...
A new MIT analysis suggests that previous studies have overestimated the amount of hurricane-induced ocean heating and its overall impact on climate. The analysis indicates that previous estimates have failed to consider how the oceans change with the seasons.