Unsurprisingly, big SUVs with big engines are bad for the environment.
Every year, some of the United Nation's brightest climate scientists come together to publish a report. Think of it as a checkup at the doctors, but for the entire human race and the planet on which we live. Typically, things don't look good. The reports generally propose several measures that we as a species might be able to take to reduce the emissions of greenhouse gasses and start to cool our rapidly-warming planet.
This year, the report's transportation chapter took special care to discuss humanity's infatuation with cars, consumption, and status symbols, as well as how all that ties in with the warming of the planet. Basically, the UN says that among other things, big SUVs have got to go. And they need to go now.
First, it's important to note that the report's chapter on transportation isn't just there to put your Kia Telluride or GMC Yukon on blast (though it can and will). The report states that how we move freight is also a huge issue. That said, the climate report also says that passenger cars, bikes, and vans contribute about 75% of passenger transport-related CO2 emissions, while mass transit (trains, busses, etc.) only accounts for about 7%. The report blames that ever-rising figure on "consumer preferences towards larger SUVs." But it's not just the fact that we like big trucks and cannot lie.
The UN's 2022 report also says that we like to buy big, wasteful, flashy things (see: Hummer EV). Hummers notwithstanding, the report goes on to state that "Status seeking can work to reduce emissions when 'green products' such as an electric car or photovoltaics on the roof become a sign for high-status," which is pretty harsh but fair.
In short, the full report calls us out for trying to consume our way into a greener lifestyle.
According to the report, 40% of vehicles sold in 2019 were the very SUVs it's calling out for being wasteful. The UN's climate scientists say that the best way to get the results posited by the report are at the policy level. That means that not only do we need to stop buying bigger, more wasteful vehicles, we also need to show policymakers that's the case. You can read the section of the report that focuses on SUVs and the climate here.