Thursday, July 18, 2024

Kids play in the cooling fountain at Harvard’s Science Center Plaza in Cambridge. (Photo: Kate Wheatley)

Cambridge is facing much higher temperatures, with predictions that the number of days above 90 degrees could almost triple by 2030 and might be the norm every day of summer by 2070. Yet the city’s ambitious plan to deal with climate change shows that protecting residents, businesses and infrastructure from excessive heat is more complicated than preventing harm from flooding and storms. And oppressive heat could be more dangerous than floods: It causes more deaths than any other element of natural disasters.

“As a city we have experienced flooding for a long, long time. There’s a mature program in place in terms of mitigating flooding,” assistant city manager and former public works commissioner Owen O’Riordan said in a telephone interview Sept. 20. “When it comes to excessive heat, Cambridge is in a different place than the tropics.” In other words, the city, like other communities in the Northeast, isn’t used to coping with steamy tropical weather.

The predictions are dire. By 2030, increased temperatures could affect Cambridge police headquarters, the city’s emergency communications center, the ambulance service ProEMS, the public health department’s main office and several schools and low-income housing developments, according to projections in the city’s Climate Change Vulnerability Assessment prepared in 2015.

“Cascading effects” from a heat-caused loss of power could be devastating, affecting “the availability of air conditioning, drinking water, lighting, refrigeration, communications and other systems that require power,” the report says.

Regularly 115 degrees by 2070

A graphic from Cambridge’s Climate Change Vulnerability Assessment gives a sense of the city’s impending heat concerns.

Most vulnerable to extreme heat are “people living below the poverty level, young children and elderly adults living alone,” the assessment said. Mapping those populations identified certain areas of North Cambridge, The Port and Riverside as most at risk. Besides that, maps show local “urban heat islands” within the city that face higher temperatures because of factors such as lack of tree cover, more impervious and heat-absorbing surfaces and older housing without adequate ventilation and air conditioning. The average heat index in those areas – in East Cambridge, North Cambridge, Central Square, Cambridgeport and MIT/Area II – could reach 100 degrees when the average in the city is 96 degrees in 2030; and could exceed 120 degrees when the city average is 115 degrees in 2070.

An effort by the city’s Community Development Department and units of the National Aeronautical and Space Agency and the American Geophysical Union, which included measuring roof reflectivity from above, produced the Cambridge Urban Heat Dashboard. It shows roof “albedo” – a number representing how well building roofs reflect sunlight, thus reducing building and area temperatures.

The dashboard reports albedo for virtually every roof in the city in 2008, 2013 and 2018. It lets users look up roof albedo at any address, and also shows neighborhood albedo levels and changes in albedo over those years. Roof reflectivity has increased during that period, mostly from nonresidential buildings. Another section of the dashboard shows the difference between ambient temperatures in the suburbs of Eastern Massachusetts and temperatures in the “urban heat islands” of Cambridge and other cities.

Getting communities to take lead

The plan for dealing with excessive heat is considerably less explicit. As outlined in Resilient Cambridge, the city’s climate change blueprint, it relies heavily on self-help by residents and actions by the private sector rather than government assistance. It calls for strategies to develop “closer communities” so that “members of the community look out for each other,” O’Riordan said. Along the same lines, the city wants to “enable people to think about what they can do to help themselves,” he said.

As an example of city efforts to foster closer ties among neighbors, O’Riordan cited the city’s invitation over the summer encouraging citizens to hold block parties, offering $200, permits and play equipment for kids. “It encourages a stronger network,” O’Riordan said. Cambridge also wants to develop “neighborhood hubs” as places to come for information and support around climate change, including high temperatures. So far it is applying for funding for one site, the Cambridge Community Center in Riverside.

Another goal is developing a “leader program identifying people who can advocate for more education around climate change,” O’Riordan said.

More trees and more roofs with high albedo could reduce temperatures, according to research. Cambridge’s Urban Forest Master Plan calls for every neighborhood to have at least 25 percent tree canopy coverage. As of 2020, when the plan was published, six neighborhoods fell below that figure: East Cambridge, MIT/Area II, Wellington-Harrington, The Port, Cambridgeport and Riverside. City spokesperson Jeremy Warnick said the city will plant at least 1,000 street trees a year in furtherance of the pledge to have 25 percent canopy coverage in each neighborhood; critics have said neglect of street trees has led to trees dying.

Miyawaki forests

The Miyawaki forest at Danehy Park in North Cambridge after two years. Photo: Biodiversity for a Livable Climate)

Recently Cambridge announced opening a park in East Cambridge with a micro-forest of almost 400 trees on less than an acre. Volunteers, aided by the city, have planted two similar tree projects, known as Miyawaki forests, in Danehy Park in North Cambridge and Green-Rose Park in The Port. Miyawaki forests, named for the Japanese botanist and plant ecologist who developed the idea, are thickly planted collections of diverse trees that grow fast, restore natural habitat and provide cooling and shade.

The urban forest plan also enlists several city agencies to help increase and preserve the city’s tree canopy, which has been shrinking. But according to the plan, the majority of trees now standing in the city – and most of those that are removed – are on private property. And for the most part, the Resilient Cambridge answer to excessive heat from climate change calls for private citizens and developers to increase the tree cover and lighten roofs and pavements. The city is nudging builders to act with new zoning rules that require large projects and substantial renovations to meet “green factor” standards that include preserving and adding trees, building vegetation-covered “green roofs” and adding canopies and other shade elements. Each project must achieve a certain “cool score” – a number made up of the development’s performance in the “cool factor” strategies – to win city approval.

The heat-related zoning requirements became effective May 23; Warnick said that so far seven projects have won Green Factor certification at the building permit or special permit and design review stages. The zoning rule mandates a separate review and certification at each stage of the approval process: before builders get a special permit, building permit and certificate of occupancy.