In short:
- There are no long term trends in Atlantic hurricane activity
- Hurricanes are not becoming more intense
- There was a marked decline in hurricane frequency during the 1970s and 80s, partly due to natural variability (AMO*) and maybe also due to reduced pollution.
- Since 1990, hurricane frequency has returned levels prior to that period of decline.
- *Atlantic Multi-decadal Oscillation
- Read the details here:
The Truth Comes Back To Haunt Bob Ward! | NOT A LOT OF PEOPLE KNOW THAT (wordpress.com)
Hurricanes may even be decreasing slightly, but are increasing in intensity. Cat 4 and 5 hurricanes are increasing in number. On the opposite end of lower intensity hurricanes they are decreasing in number. Hurricanes may not be decreasing, but they are becoming more dangerous.
ReplyDeletehttps://yaleclimateconnections.org/2019/07/how-climate-change-is-making-hurricanes-more-dangerous/
How climate change is making hurricanes more dangerous
Stronger wind speeds, more rain, and worsened storm surge add up to more potential destruction.
by JEFF BERARDELLI
JULY 8, 2019
Are hurricanes getting stronger?
The authors of that same 2013 study found a substantial regional and global increase in the proportion of the strongest hurricanes – category 4 and 5 storms. The authors attribute that increase to global heating of the climate: “We conclude that since 1975 there has been a substantial and observable regional and global increase in the proportion of Cat 4-5 hurricanes of 25-30 percent per °C of anthropogenic (human-caused) global warming.”
Interestingly, the increase in those most powerful of storms is balanced by a similar decrease in category 1 and category 2 hurricanes. The authors put forth this intriguing theory: “We suggest that this [balance] arises from the capped nature of tropical cyclones to a maximum value defined by the potential intensity, which increases only slightly with global warming.”
This is the same site and same article. When a hurricane goes over a pool of ocean water that has been increasing in temperature from human climate change, the hurricane develops quite rapidly at that point. NOAA keeps track of the ocean temperature change with the Argo Buoys. Along with other sensors, our oceans are increasing in temperature.
ReplyDeleteAre hurricanes intensifying more rapidly?
Rapid intensification, defined as an increase of wind speed of at least 35 mph in 24 hours, has recently garnered a lot of attention as a result of hurricanes like Harvey, Irma, Maria and Michael in 2017 and 2018. Examining the hurricane record in the Atlantic basin from 1986 to 2015, a recent study found rapid intensification increased 4.4 mph per decade. The study’s authors attribute most of the gains to a shift into the warmer phase of the Atlantic Multidecadal Oscillation, a natural cycle.
But the authors of a 2019 paper led by scientists at NOAA’s Geophysical Fluid Dynamics Laboratory suggest that global warming also plays a role. Using simulations from one of the most advanced climate models available, called HiFLOR, the team of researchers concludes that recent increases in rapid intensification “is outside HiFLOR’s estimate of expected internal climate variability which suggests the model’s depiction of climate oscillations like the AMO cannot explain the observed trend.”
So while the team cannot attribute the rapid intensification gains to human-caused warming, they do say human-caused warming significantly increases extreme tropical cyclone intensification rates in the HiFLOR model.
Same link again. This is a very good article based in science evidence. It is just pure physics that as the temperature of the atmosphere increases from our human pollution of GHGs, this effects how much water vapor that the atmosphere can hold. 7% increase for every degree celcius. As pointed out below, some very extreme hurricanes are coming out of this change in our climate. Texas has 60 inches of rain poured them from hurricane Harvey. A catastrophic hurricane event.
ReplyDeleteAre hurricanes producing more rain?
When it comes to the link between a warming world and weather, one of the most well-understood and robust connections is increased rainfall. Simply put, the warmer the air is, the more moisture it can hold and the more rain it produces. Generally, the increase in rainfall follows the Clausius-Clapeyron equation, which dictates that for every one degree Celsius (1.8 degrees Fahrenheit) increase, the atmosphere can hold 7% more moisture.
This increase in moisture and rainfall does not fall uniformly; in tropical cyclones this effect is boosted. In a 2018 paper about the link between increasing ocean heat content and hurricanes, lead author Kevin Trenberth of the National Center for Atmospheric Research explains that “the convergence of moisture into a storm not only leads to higher precipitation but also, for certain storms, greater intensity and growth.” So we can see that a combination of warmer air and water lead to increases in rainfall beyond the simple Clausius-Clapeyron relationship.
A good example of that is the unprecedented 60 inches of rain that fell in 2017 in southeast Texas in Hurricane Harvey. Researchers have concluded that a repeat of rainfall that intense is predicted to happen only once every 9,000 years. A majority of the rain was caused by Harvey’s extremely slow movement. But multiple attribution studies conclude that a significant amount of rain can be traced to human-caused warming, with various estimates ranging from 15% to 20% to 38%. Using the term “biblical” to describe Harvey’s rainfall, MIT’s Kerry Emanuel calculates a six-fold increase in the probability of an event of that magnitude since just the late 20th century.
Forward stalling is being detected. Is this conslusive, not yet. Hurricane Harvey stalled out over Texas and was devastating. The slower the hurricane, the more time they have to damage things.
ReplyDeleteDoes climate change affect the forward speed of hurricanes?
Some climate scientists theorize that slower steering currents resulting from a warmer climate may have contributed to Harvey’s lethargic movement. At this point, that question remains unanswered.
But a 2018 study by NOAA’s James Kossin discovered a 10% global reduction in forward speed of tropical cyclones since 1949. Even more concerning – because of the impact on flooding – is the heightened slowdown detected over land areas: 21% in the western north Pacific and 16% in the North Atlantic. Authors of another study support these concerns, finding a significant positive trend over the past several decades in coastal rainfall from tropical cyclones that stall. That study does not, however, reach a conclusion on the reason for the increased stalling.
Putting all your eggs in the basket of no increase in hurricanes just doesn't work. Hurricanes will become more dangerous with increasing warming from human pollution of GHGs. They already are now.
ReplyDeleteWhile many models do forecast a decrease in number, Emanuel’s 2013 study, using a higher-end warming scenario, found that the frequency of tropical cyclones increased in most locations. And that study is not alone. A more recent study Kieran Bhatia from NOAA GFDL, using the high-resolution HiFLOR model, shows a global increase in storm frequency of 9% and a 23% increase in the Atlantic basin by the end of the 21st century.
When asked about the conflicting research findings on cyclone frequency, Emanuel said by email: “My own view is that we really do not know at this point whether the overall global frequency of [tropical cyclones] will increase, decrease, or stay the same. It is an area of active research.”
But Emanuel stresses that the frequency metric is dominated by weak storms that typically do not do much damage, making frequency much less consequential than nailing down future intensity and rainfall.
“There is a strong consensus in the tropical cyclone climate community that the incidence of high-category events will increase, and that storms will precipitate more,” Emanuel said.
With such conflicting views it is hard to see any reliable predictions for the future. Whatever hurricanes do, we will have to deal with it. As for the role of CO2, there is no evidence that it is the main cause of global warming. There is still a lot we don't fully understand.
ReplyDelete
DeleteThe only other source of warming could be the sun. The sun as measured, hasn't changed. Our level of GHGs in the atmoshpere determines the temperature at the surface of the earth. Your premise of unknowing hasn't convinced any scientist that your reasoning has validity.
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.ipcc.ch/site/assets/uploads/2018/02/AR5_SYR_FINAL_SPM.pdf
Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems. {1} SPM 1.1 Observed changes in the climate system Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen. {1.1}
} Anthropogenic greenhouse gas emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever. This has led to atmospheric concentrations of carbon dioxide, methane and nitrous oxide that are unprecedented in at least the last 800,000 years. Their effects, together with those of other anthropogenic drivers, have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century. {1.2, 1.3.1}
Anthropogenic greenhouse gas (GHG) emissions since the pre-industrial era have driven large increases in the atmospheric concentrations of carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O) (Figure SPM.1c). Between 1750 and 2011, cumulative anthropogenic CO2 emissions to the atmosphere were 2040 ± 310 GtCO2 . About 40% of these emissions have remained in the atmosphere (880 ± 35 GtCO2 ); the rest was removed from the atmosphere and stored on land (in plants and soils) and in the ocean. The ocean has absorbed about 30% of the emitted anthropogenic CO2 , causing ocean acidification. About half of the anthropogenic CO2 emissions between 1750 and 2011 have occurred in the last 40 years (high confidence) (Figure SPM.1d). {1.2.1, 1.2.2}