"For the past three decades, Hawai'i's temperature has been growing at a rate similar to the overall global warming rate, especially at high elevations, with an increase over plus 1.4 F in the last 30 years."
"Previously, the Hawai'i temperature index had been half of the global warming rate trend."
This, according to Tom Giambelluca, a University of Hawai'i-Manoa geography professor, who has been looking at what happens when weather or vegetation patterns change on a tropical island for more than two decades, using research from stations on Maui and throughout the world.
Hawaiian Island Land Trust President Helen Nielson and Jonathan Starr, a former member of both the Maui County Water Commission and the Maui Planning Commission, joined approximately 60 people to hear a presentation on the UH Maui College campus on how changing climate and invasive plants may affect Maui’s water future.
Giambelluca told the nearly 60 audience members attending his talk that, "Changing climate global temperature has increased over the last 100 years. No doubt about that in the scientific community. It is the affect of human activity--especially greenhouse gases."
He said that despite the fact that 97 percent of scientists accept the evidence of global warming, "We don't have the political will to reduce pollution and there is a disinformation campaign by carbon-based energy producers that is based on outright lying."
The professor made his remarks as the speaker at a seminar on "How Changing Climate and Invasive Plants Affect Maui's Water Future," held last week on the UH-Maui campus and sponsored by The Sustainable Living Institute of Maui, Maui Tomorrow Foundation and the Maui County Department of Water Supply.
Despite the headline-grabbing nature of his comments, Giambelluca urged caution in interpreting the data for Maui. One reason for this is because the sampling size on Maui is small as opposed to data collected from the entire Northern Pacific area.
On Maui, rainfall declined by 8.9 percent from 1978 to 2007. Statewide the drop was 6 percent. Along with trade wind data, this may signal the beginning of a dry period on Maui, but Giambelluca noted that this might be too small a period of study to make a definite judgment.
Along with a reduction in precipitation, there has been a consistent decline in rainfall leading to a long-term decline in stream flow.
According to Giambelluca, "By end of the century, expect increasing drought frequency, for all of Molokai, Lana'i, Central, Upcountry and South Maui."
"It is certain that Maui will experience increasing temperatures and a rise in sea level," said Giambelluca,
Less certain are lower rainfall, fewer heavy rainfall events, more frequent droughts, higher rates of water evaporation, reduced stream flow and reduced groundwater recharge. But, even with the uncertainty factored in, Giambelluca said, "We are heading to a drier future."
In the near future, expect that the most significant influence on Hawai'i's weather will be the phenomenon known as "El Nio" and as "La Nia." These two weather patterns periodically form off the coast of Chile and affect the Pacific Ocean's surface water temperature. This in turn influences the weather patterns that affect Hawai'i.
Giambelluca believes that while the outlook is neutral right now, we could be heading into an El Nio period, which would mean a drier winter.
Giambelluca's teachings and research specialize in climate, climate change and eco-hydrology. He is best known for his collaboration on the "Rainfall Atlas of Hawai'i," a groundbreaking 1986 work mapping rainfall patterns for the major Hawaiian Islands.
He also studies the effect of biological invasions, particularly of alien tree species on water, soil and carbon storage.
Invasive plants, such as the strawberry guava, are also a problem associated with a precipitation change on Maui.
According to Giambelluca, areas invaded by the strawberry guava use 7 percent more water than non-invaded areas. In areas where native forests still exist and have been invaded by the strawberry guava, evaporation is occurring at a 53 percent greater rate than in non-invaded forest areas.
The concern here is evidence suggesting that temperature increases are occurring at a higher rate as the elevation increases. This can have an impact on how clouds are formed and if they will have sufficient moisture to produce rainfall.
While the overall trends are pointing toward a drier and warmer future for Maui, the devil remains in the details, with the exact affects and when and where they will occur still subject to more study.
For more information contact the Sustainable Living Institute of Maui at sustainablemaui.org.