Our People
Rainier Climate was founded in 2024 by Connie, Steve, and Sam Ballmer to accelerate solutions to the global climate crisis. Building on more than $1 billion in philanthropic investments in climate initiatives since 2022, the Ballmer family launched Rainier Climate to drive even bolder, collaborative, and scalable solutions aimed at dramatically reducing global greenhouse gas emissions. We bring a mix of strategic insight, collaborative spirit, and deep expertise to our work—partnering with changemakers around the world to accelerate high-impact solutions.

Arun Asok
Arun is the Program Director, Climate Finance for Rainier Climate. In this role, Arun focuses on using the tools of finance to encourage capital to flow to projects that deliver greenhouse gas emissions reductions at scale. Prior to joining Rainier, Arun served as Global Head of Private Capital & Impact Investing at Abt Global, and as a fund manager at Bamboo Capital Partners, where he led the launch and fundraise for the BUILD Fund—a blended finance vehicle focused on climate and gender, created in partnership with the United Nations.

Maria Carney
Maria is the Vice President of Operations for Rainier Climate. In this role, Maria is focused on creating systems, processes and culture that support Rainier in accomplishing its strategic objectives. Prior to joining Rainier, Maria served as the Director of Programs for Oxbow Farm & Conservation Center, as an operations lead (in various roles) at the Bill & Melinda Gates Foundation, and as an attorney practicing in international environmental law.

Justin Guay
Justin is the Program Director, Strategic Communications and Public Engagement for Rainier Climate. In this role, Justin focuses on building the enabling conditions that support climate action, including public and key stakeholder support. Prior to joining Rainier, Justin was a Program Director at Quadrature Climate Foundation, where he managed a portfolio of global grants focused on climate and resilience. Justin has also held senior roles in NGOs and re-granting organizations focused on finance, transport, the power sector, and other aspects of the clean energy transition.

Simon Mui
Simon is the Program Director, Transportation for Rainier Climate. In this role, Simon oversees Rainier’s grantmaking to enable the transportation sector to decarbonize while improving affordability, access, and efficiency. Prior to joining Rainier, Simon served as Managing Director for Transportation at the Natural Resource Defense Council, and has also held roles in government and the private sector.

Daniel Noll
Daniel is the Program Director, Energy Systems for Rainier Climate. In this role, Daniel leads strategies to make power and energy systems cleaner, more reliable, and affordable. Prior to joining Rainier, Daniel worked in advocacy, government, philanthropy, and the private sector supporting global energy transition programs, including most recently serving as a Senior Program Manager for Sequoia Climate Foundation.

Cassandra Serrano
Cassandra is the Executive Assistant for Rainier Climate. In this role, Cassandra supports the President and Co-Founder with tactical and strategic initiatives. Prior to joining Rainier, she provided executive support for the Ballmer Group Philanthropy. Cassandra recently completed the Master of Natural Resources program at Oregon State University, with a focus in wildlife conservation and management, renewable energy and environmental policy.

Tom Steinbach
Tom is the President of Rainier Climate. In this role, Tom drives the strategic and operational direction of the organization, with a focus on setting grantmaking priorities and building a team of experts focused on reaching net zero emissions by 2050. Prior to joining Rainier, Tom served as the Executive Director of Tempest Advisors and the Sea Change Foundation, and as Environment Program Director at the William and Flora Hewlett Foundation. Tom also serves as Climate Lead board chair, Flora Family Foundation board vice chair, and formerly served as Climate Funder Table chair.

Beth Trask
Beth is the Program Director, Super Pollutants for Rainier Climate. In this role, Beth focuses on reducing emissions of powerful and fast-acting pollutants that contribute to roughly half of current global warming. Prior to joining Rainier, Beth served as Vice President, Energy Transition at Environmental Defense Fund, where she developed initiatives to address methane and other short-lived climate forcers, improve air quality, and decarbonize the hard-to-abate sectors.

Vance Wagner
Vance is the Program Director, Industry for Rainier Climate. In this role, Vance leads Rainier’s efforts to rapidly scale sustainability solutions for the industry sector—one of the world’s largest and most diverse sources of emissions. Prior to joining Rainier, Vance worked in philanthropy, government, and civil society, including most recently serving as Vice President for Strategic Partnerships at Energy Foundation China and as China Counsellor in the Office of the Special Envoy for Climate Change at the U.S. Department of State.
Want to join our dynamic, mission-driven team? Check out our job openings on LinkedIn and learn how you can help accelerate global climate solutions.
