When a hurricane strikes land, the destruction of life and property is largely confined to a narrow coastal area. This is because hurricanes are fueled by the moisture from the ocean, [1][2][3] with the implication that hurricane intensity decays rapidly after striking land. 4,5 In contrast to the effect of a warming climate on hurricane intensification, many aspects of which are fairly well understood, 6-10 little is known of the corresponding effect on hurricane decay.Here we analyze intensity data for North Atlantic landfalling hurricanes 11 over the past 50 years and show that hurricanes decay has slowed, in direct proportion to a contemporaneous rise in the sea-surface temperature. 12 Thus, in the late 1960s, a typical hurricane lost ∼75% of its intensity in the first day past landfall; now, the corresponding decay is only ∼50%. We also show, using computational simulations, that warmer sea surface temperatures induce a slower decay by increasing the stock of moisture which a hurricane carries as it hits land. This 'storm moisture' constitutes a source of heat that is not considered in theoretical models of decay. [13][14][15] Additionally, we show that climate-modulated changes in hurricane tracks 16,17 1 contribute to the increasingly slow decay. Our findings suggest that as the world continues to warm, the destructive power of hurricanes will extend progressively farther inland.Hurricanes thrive on moisture. Moisture from warm tropical oceans fuels the intense winds of a hurricane heat engine. 2,3 In a warming world, the moisture supply is enhanced. Warmer oceans supply more moisture, and warmer air, owing to the Clausius-Clapeyron relation, 18 holds more moisture. As a result, we expect that the maximum intensity a hurricane can achieve over its lifetime increases. 6,9 Indeed, as the world warms, the strongest hurricanes (which, compared with the weaker ones, are less affected by impeding factors, e.g., wind shear) are getting stronger, with the most pronounced intensification seen for the North Atlantic hurricanes. 8 Without moisture, hurricanes wither. A landfall severs 1, 19, 20 a hurricane from the ocean, its moisture source. Consequently, the intensity decays rapidly. (When the intensity drops below 33 m/s, the hurricane, per the Saffir-Simpson scale, 21 is termed a tropical storm; however, for simplicity, we refer to tropical storms also as hurricanes.) How might the hurricane decay rates change in a warming world? In contrast to the extensive studies of hurricanes over ocean, this question has attracted scant attention.
Decay timescale, τWe study North Atlantic landfalling hurricanes (Fig. 1a) over 1967-2018 using the best-track database "Atlantic HURDAT2", 11 widely considered the most reliable database amongst all the ocean basins. (See Methods for further discussion on the data.) For each hurricane, we analyze the intensity, V , during the first day past landfall, the period over which the hurricane inflicts most
