User:Angelakhong92/Tropical cyclones and climate change

Modeling Tropical Cyclones
Climate models are used to study expected future changes in cyclonic activity. Lower-resolution climate models cannot represent convection directly, and instead use parametrizations to approximate the smaller scale processes. This poses difficulties for tropical cyclones, as convection is an essential part of tropical cyclone physics.

Higher-resolution global models and regional climate models may be more computer-intensive to run, making it difficult to simulate enough tropical cyclones for robust statistical analysis. However, with growing advancements in technology, climate models have improved simulation abilities for tropical cyclone frequency and intensity.

One challenge that scientists face when modeling is determining whether the recent changes in tropical cyclones are associated with anthropogenic forcing, or if these these changes are still within their natural variability. This is most apparent when examining tropical cyclones at longer temporal resolutions. One study found a decreasing trend in tropical storms along the eastern Australian coast over a century-long historical record.

Intensity
Tropical cyclones use warm, moist air as their fuel. As climate change is warming ocean temperatures, there is potentially more of this fuel available. A study published in 2012 suggests that SSTs may be valuable as a proxy to measure potential intensity (PI) of tropical cyclones, as cyclones are sensitive to ocean basin temperatures. Between 1979 and 2017, there was a global increase in the proportion of tropical cyclones of Category 3 and higher on the Saffir–Simpson scale, which are cyclones with wind speeds over 115 miles per hour. The trend was most clear in the North Atlantic and in the Southern Indian Ocean. In the North Pacific, tropical cyclones have been moving poleward into colder waters and there was no increase in intensity over this period. With 2 °C warming, a greater percentage (+13%) of tropical cyclones are expected to reach Category 4 and 5 strength.

Frequency
A study published in 2015 concluded that there would be more tropical cyclones in a cooler climate, and that tropical cyclone genesis is possible with sea surface temperatures below 26 °C.With warmers sea surface temperatures, especially in the Southern Hemisphere, in tandem with increased levels of carbon dioxide, it is likely tropical cyclone frequency will be reduced in the future.

Storm surges and flood hazards
Additional sea level rise will increase storm surge levels. It is plausible that extreme wind waves see an increase as a consequence of changes in tropical cyclones, further exacerbating storm surge dangers to coastal communities. Between 1923-2008, storm surge incidents along the US Atlantic coast showed a positive trend. A 2017 study looked at compounding effects from floods, storm surge, and terrestrial flooding (rivers), and projects an increase due to climate change. However, scientists are still uncertain whether recent storm surges are a response to anthropogenic climate change.

United States
In the United States, there have been several concrete initiatives taken to better prepare for the strengthening of hurricanes, such as preparing local emergency shelters, building sand dunes and levees, and reforestation initiatives. Despite better modeling capabilities of hurricanes, property damage have increased dramatically. The National Flood Insurance Program incentivizes people to re-build houses in flood-prone areas, and thereby hampers adaptation to increased risk from hurricanes and sea level rise. Due to the wind shear and storm surge, a building with a weak building envelope is subject to more damages. Risk assessment using climate models help determine the structural integrity of residential buildings in hurricane-prone areas.

Some ecosystems, such as marshes, mangroves, and coral reefs, can serve as a natural obstacle to coastal erosion, storm surges, and wind damage. These natural habitats are seen to be more cost-effective as they serve as a carbon sink and support biodiversity of a region. Although there is substantial evidence of natural habitats being the more beneficial barrier for tropical cyclones, built defenses are often the primary solution for government agencies and decision makers. A study published in 2015, which accessed the feasibility of natural, engineered, and hybrid risk-mitigation to tropical cyclones in Freeport, Texas, found that natural ecosystems could reduce flood heights and ease the cost of built defenses in the future.