New Video: Hot Ocean, Hurricanes, Houston, and Harvey

Kevin  Trenberth has a new paper, measuring the change in ocean heat content in the Gulf of Mexico as Hurricane Harvey passed over.  Turns out the heat-loss just matches the energy of precipitation that made Harvey an unprecedented catastrophe.

Dr. Trenberth’s co-authors Lijing Cheng of China’s Institute of Atmospheric Physics, and Peter Jacobs of George Mason University round out this explainer. Short and powerful demonstration of how scientists more and more understand the link between a warming planet and specific extreme events.

I hope to post more soon from the brilliant interviews I captured for this piece – Lijing Cheng and Peter Jacobs are climate comms stars.

Hurricane season starts tomorrow.

National Center for Atmospheric Research:

BOULDER, Colo. — In the weeks before Hurricane Harvey tore across the Gulf of Mexico and plowed into the Texas coast in August 2017, the Gulf’s waters were warmer than any time on record, according to a new analysis led by the National Center for Atmospheric Research (NCAR).

These hotter-than-normal conditions supercharged the storm, fueling it with vast stores of moisture, the authors found. When it stalled near the Houston area, the resulting rains broke precipitation records and caused devastating flooding.

“We show, for the first time, that the volume of rain over land corresponds to the amount of water evaporated from the unusually warm ocean,” said lead author Kevin Trenberth, an NCAR senior scientist. “As climate change continues to heat the oceans, we can expect more supercharged storms like Harvey.”

Despite a busy 2017 hurricane season, Hurricane Harvey was more or less isolated in location and time, traveling solo over relatively undisturbed waters in the Gulf of Mexico. This gave Trenberth and his colleagues an opportunity to study in detail how the storm fed off the heat stored in that 930-mile wide ocean basin.

The team compared temperatures in the upper 160 meters (525 feet) of the Gulf before and after the storm using data collected by Argo, a network of autonomous floats that measure temperature as they move up and down in the water. To measure rainfall over land, the scientists took advantage of a new NASA-based international satellite mission, dubbed Global Precipitation Measurement.

Weather.com:

As tropical cyclones feed on latent heat, ocean temperatures cool in the vicinity of the storm as heat is lost.

Trenberth and his research team found that the heat loss in the Gulf of Mexico during Harvey matched the latent heat released by the hurricane’s rainfall along the Gulf Coast, concluding that the latent heat fueled the storm.

“Without so much ocean heat and moisture supply, the rainfall would not have been anything like as much,” Trenberth said in a news release summary Tuesday. “In this way, a direct link to global warming from human-induced heat-trapping gases in the atmosphere is established.”

The paper added that hurricanes play a key role in the Earth’s climate system: they pump heat out of the warm tropical oceans, keeping water temperatures cooler. Once that heat enters the atmosphere, it’s dispersed by the wind and can eventually be radiated into outer space.

“In this way, the hurricanes act as a relief valve for the ocean; they result in somewhat cooler conditions but at the expense of a severe storm,” Trenberth said.

The paper noted that planning for supercharged hurricanes, such as Harvey, is essential. This should include updating building codes, electrical systems and flood-control systems, preparing more evacuation routes and planning for long-term power outages.

However, the authors concluded that these improvements may not be adequate in many areas, including Texas, Florida and Puerto Rico – some of the hardest-hit areas during Harvey, Irma and Maria last year.

“Proactive planning for the consequences of human-caused climate change is not happening in many vulnerable areas, making the disasters much worse,” said Trenberth.