Company lists · Data refreshed September 2026

Top 25 Climate change consultants based in the United States

RevenueBase identified 1,224 climate change consultants headquartered in the United States as of September 2026 and tracks 20,933 professional contacts across them, including 9,211 with verified work emails. New York is the largest hub.

This list covers climate change consultants headquartered in the United States, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 21, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 21, 2026 86% judged on-target in blind review
1,224Companies
20,933Contacts tracked
9,211Verified emails
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The 25 largest climate change consultants based in the United States

Ranked by team size
Top 25 of 1,224 climate change consultants based in the United States, ranked by team size, largest first. Data refreshed Sep 21, 2026. RevenueBase Smart Search rates how each company's information relates to climate change consultants: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#CompanyRevenueBase Smart SearchHeadquartersEmployeesContacts
1Indirect evidenceBaton Rouge, LA, United StatesHQ checked Sep 21, 20261,001-5,0002,639 contacts →

Indirect evidence

“APTIM enhances the quality of the environment, wellbeing of people, resilience of communities, and opportunity for employees to make a difference, not just a living.”

Source: RevenueBase Database · checked Sep 21, 2026
2Indirect evidencePhoenix, AZ, United StatesHQ checked Sep 21, 20261,001-5,0001,629 contacts →

Indirect evidence

“Founded on a commitment to sound science and creative solutions, SWCA is a leader in environmental and management consulting services.”

Source: RevenueBase Database · checked Sep 21, 2026
3Indirect evidenceAustin, TX, United StatesHQ checked Sep 21, 2026n/a1,145 contacts →

Indirect evidence

“OLA Sustainability, LLC OLA Sustainability is a consulting firm that focuses on integrating sustainable practices into commercial and multifamily design projects.”

Source: RevenueBase Database · checked Sep 21, 2026
4Indirect evidenceTampa, FL, United StatesHQ checked Sep 21, 20261,001-5,0001,139 contacts →

Indirect evidence

“At Verdantas, we blend engineering and environmental science together with advanced technology and world-renowned labs to create solutions with the big picture in mind.”

Source: RevenueBase Database · checked Sep 21, 2026
5Partial evidenceSan Francisco, CA, United StatesHQ checked Sep 21, 2026n/a759 contacts →

Partial evidence

Climatebase is the community for climate & sustainability professionals, and the world's #1 platform for green jobs.”

Source: RevenueBase Database · checked Sep 21, 2026
6Indirect evidenceSan Francisco, CA, United StatesHQ checked Sep 21, 2026501-1,000732 contacts →

Indirect evidence

“ESA is a 100% employee-owned environmental consulting firm.”

Source: RevenueBase Database · checked Sep 21, 2026
7Indirect evidenceBurlington, MA, United StatesHQ checked Sep 21, 2026501-1,000535 contacts →

Indirect evidence

“For 35 years we have been helping investors, lenders, owners, developers, contractors, and property managers reduce risk and optimize their built facilities, infrastructure and…”

Source: RevenueBase Database · checked Sep 21, 2026
8Indirect evidenceWashington, DC, United StatesHQ checked Sep 21, 202651-200434 contacts →

Indirect evidence

“Synergy Consulting is Global Leader in Financial and Corporate Advisory.”

Source: RevenueBase Database · checked Sep 21, 2026
9Indirect evidenceIrvine, CA, United StatesHQ checked Sep 21, 2026201-500383 contacts →

Indirect evidence

“We are Trio – built from Edison Energy, Alfa Energy, and Altenex Energy.”

Source: RevenueBase Database · checked Sep 21, 2026
10Indirect evidenceLong Beach, CA, United StatesHQ checked Sep 21, 2026201-500375 contacts →

Indirect evidence

“P2S has brought forward-thinking, sustainable engineering solutions to California, the Pacific Northwest, and beyond, for over 30 years.”

Source: RevenueBase Database · checked Sep 21, 2026
11Indirect evidencePark Ridge, NJ, United StatesHQ checked Sep 21, 2026201-500336 contacts →

Indirect evidence

“National Utility Service, Inc.”

Source: RevenueBase Database · checked Sep 21, 2026
12Indirect evidenceGainesville, FL, United StatesHQ checked Sep 21, 2026201-500305 contacts →

Indirect evidence

“Environmental Consulting & Technology, Inc.(ECT) is a multi-disciplinary environmental and sustainability consulting firm delivering strategy, permitting, design, and management…”

Source: RevenueBase Database · checked Sep 21, 2026
13Indirect evidenceBaton Rouge, LA, United StatesHQ checked Sep 21, 202651-200305 contacts →

Indirect evidence

“CSRS was acquired by Westwood Professional Services on June 30, 2025.”

Source: RevenueBase Database · checked Sep 21, 2026
14Indirect evidenceSan Francisco, CA, United StatesHQ checked Sep 21, 202651-200288 contacts →

Indirect evidence

“CPI is an analysis and advisory organization with deep expertise in finance and policy.”

Source: RevenueBase Database · checked Sep 21, 2026
15Indirect evidenceLancaster, NY, United StatesHQ checked Sep 21, 20265,001-10,000278 contacts →

Indirect evidence

“E&E is now WSP USA.”

Source: RevenueBase Database · checked Sep 21, 2026
16Indirect evidenceSt. Louis Park, MN, United StatesHQ checked Sep 21, 2026201-500264 contacts →

Indirect evidence

“Nova Group, GBC is an international, multidisciplinary advising firm providing environmental, engineering and energy services throughout North America and around the globe.”

Source: RevenueBase Database · checked Sep 21, 2026
17Indirect evidencePittsfield, ME, United StatesHQ checked Sep 21, 2026201-500218 contacts →

Indirect evidence

“At Kleinschmidt, we work primarily with energy companies and government agencies in North America to protect and enhance the environment without compromising performance.”

Source: RevenueBase Database · checked Sep 21, 2026
18Indirect evidenceFairfax, VA, United StatesHQ checked Sep 21, 2026201-500214 contacts →

Indirect evidence

“PEG presents a comprehensive capacity for the evaluation and understanding of a broad base of energy and environmental sustainability related programs, policies and initiatives.”

Source: RevenueBase Database · checked Sep 21, 2026
19Indirect evidenceOakland, CA, United StatesHQ checked Sep 21, 2026201-500166 contacts →

Indirect evidence

“Terraphase offers cost-effective solutions to complex environmental and engineering challenges.”

Source: RevenueBase Database · checked Sep 21, 2026
20Indirect evidenceCosta Mesa, CA, United StatesHQ checked Sep 21, 202651-200165 contacts →

Indirect evidence

“HJI Group serves the global community.”

Source: RevenueBase Database · checked Sep 21, 2026
21Indirect evidenceCambridge, MA, United StatesHQ checked Sep 21, 202651-200163 contacts →

Indirect evidence

“IEc is an environmental consulting firm with four decades of experience providing consulting services to a diverse client base.”

Source: RevenueBase Database · checked Sep 21, 2026
22Indirect evidenceSan Francisco, CA, United StatesHQ checked Sep 21, 202651-200156 contacts →

Indirect evidence

“Energy.”

Source: RevenueBase Database · checked Sep 21, 2026
23Indirect evidenceIndianapolis, IN, United StatesHQ checked Sep 21, 202651-200152 contacts →

Indirect evidence

“Founded in 1988, KERAMIDA is a multidisciplinary Sustainability, EHS & Engineering consulting firm grounded in evidence-based research and development.”

Source: RevenueBase Database · checked Sep 21, 2026
24Indirect evidenceNew York, NY, United StatesHQ checked Sep 21, 202611-50133 contacts →

Indirect evidence

“At OnePointFive we solve your sustainability focused business challenges by empowering your organization with expert-led solutions, embedded training, and cutting edge tools to…”

Source: RevenueBase Database · checked Sep 21, 2026
25Indirect evidenceSeattle, WA, United StatesHQ checked Sep 21, 202651-200110 contacts →

Indirect evidence

“Cascadia Consulting Group is a majority women-owned consulting firm specializing in environmental and sustainability solutions.”

Source: RevenueBase Database · checked Sep 21, 2026

Showing 25 of 1,224 climate change consultants based in the United States

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Climate change consultants based in the United States at a glance

As of Sep 21, 2026
44.0%Verified-email coverage
17.1Average contacts per company
1-10Median size (employees)
6.0%Largest-city concentration · New York
Sep 21, 2026Page data refreshed

Companies by employee count

1-10
891
11-50
248
51-200
59
201-500
13
501-1,000
5
1,001-5,000
6
5,001-10,000
1

Email recency for this list is measured worldwide rather than for United States, so it is reported there. Company counts and contact totals on this page are exact for United States, over 1,224 companies.

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among climate change consultants, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.

Source
The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
What qualifies
Companies headquartered in the United States whose own description of what they do matches “climate change consultants”. Matching reads each company's description, not its industry code or its name.
RevenueBase Smart Search
RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names climate change consultants), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
What we exclude
Companies whose own description does not clearly place them among climate change consultants, and records with no verified work email. Companies headquartered outside United States are excluded even when they keep an office there.
Match quality
In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
Ranking
Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification
Every listed company carries at least one verified work email, 9,211 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh
This page's figures were pulled from the company graph on September 21, 2026. Lists refresh periodically as the graph is re-checked.
Corrections
Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Frequently asked

What is RevenueBase Smart Search?

RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names climate change consultants, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.

How many climate change consultants are there based in the United States?

RevenueBase identified 1,224 climate change consultants headquartered in the United States as of September 2026, matched on each company's own description of what it does rather than its industry code.

What is the largest company on this list?

APTIM, headquartered in Baton Rouge, tops this list with the largest team on record.

Which city has the most climate change consultants?

New York leads with 73 headquartered companies, followed by Washington (61) and Chicago (37).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 9,211 verified decision-maker contacts tracked across these 1,224 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 21, 2026.

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About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.