Conspiracy theory eh, nice try.You like your conspiracy theories, don't you?
Alternatively, the atmosphere is a) increasing in CO2 b) increasing in average temperature c) accelerating over the last couple of centuries, far faster than in any previous "natural cycle".
Science doesn't care if you're Ayn Rand or Vladimir Lenin; it's all about repeatable experiments. It doesn't care if you insist that nothing to see here, move along now; or "if in danger, or in doubt; run in circles, scream and shout". The measurements indicate that the temperature is rising, and so is the sea level (slowly).
Shouting at the scientists because you don't want to believe what they're saying, just makes you look... like Jeremy Corbyn and his mates. Utterly unwilling to face facts, totally convinced that they're correct in the face of all the evidence.
More like conspiracy fact, it was a theory many moons ago, circa UN Agenda 21
Combat climate change by taxing carbon instead of salaries, UN chief urges
and of course, the from non other than the UN
Pave Way For Carbon Taxation as Major Global Trend, Secretary-General Urges Finance Ministers’ Climate Meeting, Noting Emissions’ Pricing Raised $44 Billion in 2018 | Meetings Coverage and Press Releases
If you really want a conspiracy theory
Reducing carbon really means reducing population.
We will see how long that one remains a theory.
Also, climate science is not defacto, as we all know science is ever changing.
We will see how this defacto science evolves.
Of course, anybody who will not accept that it will change and may not support their cult, will of course claim it's a conspiracy.