Transcript Low confidence

Global Tropical Cyclones
Ryan N. Maue
Research Meteorologist
WeatherBELL Analytics
October 30, 2015
2005-2007
Tropical Cyclone Climatology
• What is normal for global tropical cyclone (TC)
activity? (80-90 TS per annum)
• How to quantify TC activity with our current besttrack quality? Uncertainty.
• For climate (change), what is important? Ratios,
counts, integrated metrics, SST impact, etc.
• What are the relevant metrics ?
– Landfalls
– Category 5s
IPCC, 2012: Managing the Risks of Extreme Events and Disasters
to Advance Climate Change Adaptation. A Special Report of
Working Groups I and II of the Intergovernmental Panel on
Climate Change (Field et al. 2012)
Low confidence that any observed long-term (i.e., 40 years or more) increases
in tropical cyclone activity are robust, after accounting for past changes in
observing capabilities.
The uncertainties in the historical tropical cyclone records, the incomplete
understanding of the physical mechanisms linking tropical cyclone metrics to
climate change, and the degree of tropical cyclone variability provide only low
confidence for the attribution of any detectable changes in tropical cyclone
activity to anthropogenic influences.
There is low confidence in projections of changes in tropical cyclone genesis,
location, tracks, duration, or areas of impact. Based on the level of consistency
among models, and physical reasoning, it is likely that tropical cyclone related
rainfall rates will increase with greenhouse warming.
It is likely that the global frequency of tropical cyclones will either decrease or
remain essentially unchanged. An increase in mean tropical cyclone maximum
wind speed is likely, although increases may not occur in all tropical regions.
Global Tropical Cyclone ACE
24-month Running Sums | January 1970 - October 2015
Global
NH
2
ACE  104  vmax
[knots2]
Daily Caller
Global Tropical Cyclone Frequency
12-month Running Sums TC (34 knots +) & HURR (64 knots +)
μ = 87 | 47
Global Tropical Cyclone Frequency
12-month Running Sums HURR (64 knots +) & MAJOR HURR (96 knots +)
Historical global tropical cyclone landfalls: 1970-2010
Historical global tropical cyclone landfalls: 1970-2010
Relevant metric: global major hurricane landfall$
…this subset of storms is a function of “climate”
Weinkle et al. (in press, J Climate)