Start here: the nuts & bolts of climate change
Summary
Over the 4.5 billion years of Earth’s existence due to natural climate forcings the climate had shifted between warm ‘hothouse’ and cold ‘icehouse’ states. In the last few million years the main climate forcing has been Earth’s wobbly orbit around the sun (see How to start an Ice Age). Today, that natural climate forcing is slowly cooling Earth. But anthropogenic (man-made) climate forcings—primarily through burning staggering quantities of fossil fuels—are so powerful that they’ve vastly overwhelmed the natural cycle (Fig. 1). As a consequence, Earth is warming faster than at any time since an asteroid took out the dinosaurs.
Those claiming that climate change is a hoax, a cult, or is ‘just a cycle‘ must also explain how Earth’s orbit has suddenly changed, and why the well-understood laws of physics and chemistry that underpin most aspects of modern civilization—from cars, planes, and satellites to computers, mobile phones and the Internet—are also a hoax or cult.
What’s covered on this page:
What exactly are ‘climate forcings’?
Energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another.
One way to think of this is what happens when several people push a very large stool from opposite directions. If they all apply an equal force (energy) on both sides, the stool won’t move. If those on one side pushes too hard (increasing energy), the stool becomes unbalanced, reaches a tipping point, and the tips over.
Anthropogenic (human-made) climate forcings are now pushing so hard that they’re overwhelming all of the natural cooling forcings (Fig. 2). The geological record shows that once climate tipping points are reached, the climate becomes unstable for thousands of years before a new stable ‘hothouse’ state is reached.
Where is all this extra heat going?
The imbalance leads to energy accumulation in the atmosphere, oceans and land, and melting of the cryosphere, resulting in increasing temperatures, rising sea levels, and more extreme weather. – Mauritsen et al 2025
Worryingly, the observed energy imbalance is rising much faster than expected, reaching 1.8 W/m2 in 2023—or twice that predicted by climate models—after having more than doubled within just two decades. –op.cit. (Fig. 2)
Then surface air temperatures jumped in late 2023, leading to 2024 being the first year on record to exceed 1.5°C (Fig. 4). This was partly due to El Niño, part of the natural cyclic ENSO phenomena that releases some of the heat stored in the Pacific Ocean into the atmosphere. This warming effect is known to cause temporary temperature spikes above ‘average’. In the past, cooling La Niñas, the flip side of ENSO, brought temperatures back down. That’s no longer the case:
“Cool” years are now hotter than the “warm” years of the past: tracking global temperatures through El Niño and La Niña. – Our World in Data, 2025
The carbon budget
So why had Earth’s energy imbalance suddenly increased? Was the IPCC modelling wrong?
Under the 2015 Paris Accord, the aim was to hold global warming to ‘well below 2°C’ above pre-industrial levels and to ‘pursue efforts to limit it to 1.5°C’. To do so required knowing how much additional CO2 could still be emitted into the atmosphere before those limits were exceeded. The budget, created and monitored by Global Carbon Budget, included how much was being emitted (‘spent’) and how much the planet was absorbing (‘saved’). This budget underpinned the Paris Accord as it enabled the global carbon trading market.
Most of the carbon market depended on plants absorbing CO2. If not for plants, atmospheric CO2 and with it, temperatures, would be much higher (see Greenhouses gases and how they work). Plants on land and in the ocean (mostly algae) were absorbing 38% of the excess CO2 being emitted into the atmosphere (Fig. 5). Plants also store CO2 in the soil and the bottom of the ocean where it accumulates and is recycled over millions of years.
However, warnings of a tipping point being breached were made clear at COP26 in Glasgow in 2021:
The only reason why the IPCC provides the world with the remaining carbon budget of roughly 4-500 gigatonnes, is that the models assume that the carbon sink capacity of intact nature will continue. So not only are we assuming that biological systems will not cross tipping points, we’re also assuming that the stocks of carbon in forests in soils, in wetlands and permafrost, remain reasonably intact over the next 50 years.
That is quite an optimistic assumption because it means we need to invest in conserving the remaining intact ecosystems. – Rockström, 2021 (YouTube)
Earth’s ability to absorb CO2 compromised
Then in 2023-24 the amount of CO2 in the atmosphere suddenly increased:
Concentrations [of CO2] surged by a record 3.5 ppm from 2023 to 2024, the largest single-year jump since modern record-keeping began in 1957. – World Meteorological Association (WMO) 2025
Human emissions were still climbing in 2023-2024. But based on the IPCC modelling and the carbon budget, they weren’t nearly enough to account for the increase in the energy imbalance (Fig. 1), the sudden jump in CO2 in the atmosphere, and the abrupt increase in temperatures (Fig. 4).
In 2026 a peer-reviewed paper by Dang et al showed that between 2014 and 2023 the land had been absorbing and average 3.22Gt/year of carbon. Then in 2024 the land had suddenly stopped absorbing ~30% of the CO2 that it had done so over the previous 10 years of measurements. Dang et al also pointed out what Rockström and others had been saying for years but were ignored. The 6% of heat that the land had been taking up was driving up ground surface temperatures, increasing soil respiration, and triggering decomposition of soil organic matter—which releases CO2 in a positive feedback effect.
….the underlying mechanism for the reduction was caused by hotter and drier conditions leading to a larger increase in respiration than photosynthesis….These results challenge previous assumptions about the long-term stability of the terrestrial carbon sink. – Dang et al April 2026
The land has not just stopped absorbing as much CO2 as it once had. It’s also emitting some of the ‘banked’ CO2 into the atmosphere through melting permafrost, drought, increasing wildfires, and the ongoing destruction of forests.
The consequences
The goal to keep temperatures under 1.5°C was to avoid irreversible tipping points. By definition, there is no returning to the once stable climate that enabled and sustains our modern civilization. This was acknowledged by the U.N in September 2026.
Limiting global warming to 1.5°C remains a cornerstone of the Paris Agreement, yet under current policies and alternative near-term trajectories, exceedance of 1.5°C is now widely assessed as unavoidable…There will be no going back to how things were. Some losses will be irreversible, which means returning to 1.5 doesn’t mean we return back to the same world we left. – United Nations 02 September 2026
