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BY Tali Aaron : December 15

Climate action plans (CAP) are key to cities’ ability to reduce Greenhouse Gas Emissions

AECOM SSIM software

Cities and counties are facing new challenges as federal and state regulators adopt greenhouse gas emission reductions targets and other new environmental performance standards to try to reverse the degradation of our environment and planet. We are entering an era of broad scale environmental accountability.

Achieving sustainability performance targets across complex and integrated social, ecological and economic systems such as cities and counties requires new ways of engineering the way we interact with the environment. In turn, ecologically engineering the built environment requires new quantitative performance approaches to planning. It requires understanding and analyzing the complex, systemic relationships between the built and natural environment, and capitalizing on the efficiencies that can be found through “whole systems” integrated design.

Against this backdrop, the evolution of regulations mandating reductions in greenhouse gas (GHG) emissions and climate change adaptation planning such as California’s pioneering Assembly Bill (AB) 32 and Senate Bill (SB) 375 have lead to increased pressure for both developers and governmental entities to better understand and adopt whole systems planning and design of new communities - and retrofit existing ones - that reduce GHG and achieve higher levels of environmental performance.

To prepare for the implementation of AB 32 and SB 75, many cities across California are focused on creating climate action plans (CAPs) that provide both broad strategies and specific measures to reduce their carbon footprints. AB 32 (an overarching climate change bill) and SB 375 (implementing legislation for AB 32 that focuses on transportation and land use) are tandem measures signed into law by Gov. Schwarzenegger that require California to reduce its greenhouse gas emissions to 1990 levels by 2020. The two measures put California at the forefront of battling global warming in the US.

Developing a climate action plan for a large, complex project or area is a daunting task. The permutation of combinations of efficiency measures, technologies and products over multiple land uses, building types and densities is unlimited and overwhelming for any developer or city staff. Often, financial resources are placed in areas that are easiest to understand and trendy rather than where they provide the best cost/benefit or add to an overall balanced approach. Ecological and longer term strategies often are the hardest to quantify and weigh against other, more tangible hardware-oriented measures.

The Sustainable Systems Integration Model (SSIM) is a modeling tool developed by AECOM for rationally evaluating, balancing and costing a wide variety of carbon reduction strategies to determine those best suited to meet a jurisdiction’s economic and social objectives. With countless energy and mobile emissions practices and technologies to choose from, AECOM saw the need for a modeling platform to inform jurisdictions of the combination of strategies and measures that would achieve the largest percentage GHG reduction at the lowest cost to taxpayers, businesses and residents.

By modeling sustainability performance and costs of various measures at the building, district, and community scale, SSIM is a powerful tool to construct a sound, defendable and cost-effective whole systems sustainability program. Organized around core themes of mobility, energy, water, building technology, and carbon sequestration, SSIM starts by utilizing a GIS based modeling tool to compare the sustainability merits of alternative land use solutions for those areas of a jurisdiction undergoing comprehensive plan or specific/master plan modifications. The urban form of each land use alternative is evaluated through a variety of indicators to ascertain which has the lowest inherent carbon footprint, highest trip capture, connectivity, land use balance, etc. This is done using a business as usual (BAU) scheme as a straw man, and then comparing key performance indicators such as energy, vehicle miles traveled (VMT), and GHG emissions between the plans until ultimately, a preferred plan evolves. This allows the jurisdiction to seek a fundamentally higher level of sustainability based on land use mix, transportation structure, and plan form prior to applying additional carbon reduction measures.

The standard CAP process logically provides a comprehensive list of strategies that is relatively simple, prioritized, and generally cost effective. The primary shortcoming is that although it is based on empirically-based research, its findings are not highly site-specific, and are relatively general in detail. SSIM provides a more finely-tuned, accurate, and implementable approach that expands the selection of strategies, looks at multiple levels of performance within each strategy, allows an unlimited number of combinations to be reviewed and evaluates not only cost impacts to the jurisdiction, but also to private development, home affordability, and other cost impact centers.

One aspect of the SSIM approach is that it places ecologically based carbon sequestration strategies side by side with energy, water, and mobility strategies. This is done by quantifying carbon absorption rates of various plant materials and measuring the benefits of increasing landscapes, street trees, community gardens, wetland reclamation areas, and even community gardens so that these ecological assets can be counted and included to create a more comprehensive and holistic GHG reduction strategy. This ecological services optimization approach is often found to be one of the most affordable GHG offset mechanisms available.

Complete, precise, and comprehensive modeling of man-made and natural systems on jurisdictions and large districts is extremely difficult due to their complexity and our current elementary understanding of complex natural systems. However, acknowledging those we do understand and tracking obvious linkages between systems can give a more complete picture of the offsetting and compounding impacts of prospective sustainability strategies. Recent definitions of sustainability underscore the importance of balance between the physical, social and economic dimensions. Modeling approaches similar to SSIM allow ecosystem integrity and services aspects to stand side by side with conventional mechanical and operational GHG reduction strategies and result in a more robust and affordable climate action plan.

We are in a fast-moving world where protecting our planet has taken on new and critical urgency. But even with the ever-changing complexities of the sustainability movement, we believe that the preparation of a CAP today will allow a city or county to set the stage and help define the sustainable landscape as other jurisdictions in the region seek to comply with such regulations as AB 32, SB 375, and other sustainability initiatives in the coming years. Now is the time to be a leader, not a follower.


Steve Kellenberg is an AECOM principal and can be reached at [email protected] Jeff Henderson is an AECOM senior project manager and planner and can be reached at [email protected]

8 Responses to Climate action plans (CAP) are key to cities’ ability to reduce Greenhouse Gas Emissions

  1. buildaroo on November 13, 2012 at 1:02 pm

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  2. buildaroo on October 18, 2012 at 11:40 pm

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  3. buildaroo on December 20, 2011 at 4:49 pm

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  4. Omar Masry on July 31, 2011 at 3:44 am

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  5. buildaroo on July 31, 2011 at 2:17 am

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  6. buildaroo on June 28, 2011 at 7:58 am

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  7. buildaroo on February 1, 2011 at 10:34 am

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  8. [...] 2006 California environmental law known as AB32 has become the target of businesses concerned about higher energy costs. The law, one of the most [...]

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