Scientists don't speak in gigatonnes at dinner parties. This page translates what the IPCC, the Global Carbon Project, and the Climate Action Tracker actually say — degrees of warming, tons in the air, years left — into heat you can imagine, cars you can picture, and four futures you can choose between. Every figure has a receipt at the bottom.
CO₂ in the atmosphere, autumn 2026. The May 2026 seasonal peak hit 432 ppm — a new record. In 1958 it was 313 ppm.
CO₂ humanity emits per year (38.1 Gt fossil fuels + ~4 Gt land use). Fossil emissions rose 1.1% in 2025 — another record.
Human-caused warming so far (2024). The planet is already living inside the lower edge of these charts.
From the IPCC's Sixth Assessment Report. These are global averages — your city will vary. Click a level.
Nobody can picture a gigatonne. So here's the exact same number, wearing clothes you recognize. The math is shown — check it.
That's how many average cars would have to sit idling, 24 hours a day, 365 days a year, to match what humanity actually emits. Every year. Here's the arithmetic:
~5.3 kg CO₂/hr~46.7 tonnes CO₂ per idling car per year≈ 900 million cars idling nonstop
Empire State Buildings of pure CO₂ every hour (4.8M tonnes/hr ÷ ~2,080 tonnes per building-volume at 1.98 kg/m³)
Olympic swimming pools of CO₂ every second (1,330 tonnes/s ÷ ~4.95 tonnes per pool-volume)
average cars' entire yearly driving emissions, every single day (115M tonnes/day ÷ 4.6 t/car/yr, EPA)
The "carbon budget" is how much more CO₂ we can emit before a temperature limit is likely blown. At ~42 Gt/year, the budgets drain in real time — this countdown is live.
Budget: 130 GtCO₂ from Jan 2025 (50% likelihood, IGCC 2025). Spent so far: — Gt.
Budget: 1,050 GtCO₂ from Jan 2025 (50% likelihood, IGCC 2025). Spent so far: — Gt.
Scientists measure habitability with the wet-bulb temperature — heat plus humidity. At a wet-bulb of 35°C (95°F), sweat stops cooling the body; even a healthy person in shade lasts only hours (Sherwood & Huber). Research in Nature Climate Change found Gulf cities (Doha, Dubai, Abu Dhabi) could cross that line before 2100 on a high-emissions path — and newer work shows parts of South Asia, home to 1.5 billion people, edging toward it even sooner.
There is no single year the world becomes "unbearable" — it's a map, not a date. But the geography of the unsurvivable expands with every tenth of a degree. On our current 2.6°C path, deadly humid-heat zones that are rare today become routine in the Gulf, South Asia, and parts of the US Southeast by late century. Staying under 2°C keeps most of them theoretical.
Same planet, four choices. Warming above the pre-industrial average, 2025 → 2100. Pathways drawn from Climate Action Tracker's November 2025 assessment and IPCC AR6 — stylized, but the endpoints are the published numbers.
China (~32% of fossil CO₂) and the United States (~13%) together produce roughly 45% of the world's fossil carbon. No climate math works without both of them — and no two countries have more to gain from cooperating: China manufactures the world's clean tech, America still leads in deep-tech R&D and finance. Here's a concrete joint program. Optimistic, with receipts.
Steel is ~7–8% of global CO₂. Build a joint hydrogen-direct-reduction steel program: shared pilot plants in Inner Mongolia (wind-rich) and Texas (sun + gas infrastructure being repurposed).
Drawdown: ~2 GtCO₂/yr if global steel converts by 2050.
Mutual licensing recognition for small modular reactors: a reactor certified in one country gets an accelerated path in the other. Joint gigafactories for reactor pressure vessels and fuel.
Drawdown: every 1 GW of nuclear displaces ~5 MtCO₂/yr from coal. 500 GW = 2.5 Gt/yr.
A joint 1-gigatonne-per-year direct-air-capture program by 2045 — sited in the Gobi and the American Southwest (cheap sun, empty land, basalt geology for mineralization). Shared R&D pool, split construction.
Drawdown: 1 GtCO₂/yr of verified removal — the "deploy everything" curve made real.
Methane is 80× more potent than CO₂ over 20 years, and leaks are the cheapest cuts available. Launch a joint methane-surveillance satellite constellation with automatic, public, attributed leak data — and a bilateral agreement to fine domestic leakers both countries.
Drawdown: cutting oil & gas methane 75% ≈ 0.1°C of avoided warming by 2050 (IEA) — the fastest lever on Earth.
A bilateral patent commons for batteries, electrolyzers, and grid software: any company from either country can license the pooled IP royalty-free if it manufactures in a developing country. Turns the US-China tech rivalry into a deployment race where the Global South wins.
Drawdown: indirect but enormous — every year of faster global clean-tech deployment is ~0.5–1 GtCO₂ not emitted.
A $500B joint fund to build clean grids across Africa and Southeast Asia before they lock in coal — the places where the next trillion tonnes of CO₂ will either happen or not. Co-governed, procurement split 50/50.
Drawdown: avoids ~5–10 GtCO₂/yr of lock-in by 2040 — the highest-leverage dollars in climate.
Pool ITER-scale funding into a joint commercial fusion demonstration by 2040, plus the engineering studies for intercontinental HVDC "supergrids" that move solar power across time zones.
Drawdown: the century-scale prize — effectively unlimited clean firm power. No honest number yet; that's why it's a moonshot.
If the two countries that produce nearly half the world's carbon build the green future together, every other country gets a template, a supply chain, and political cover. Rivalry got us the Space Race. Cooperation gets us the planet.
See the mega-projects →Figures collected October 2026. "Est." labels mark proposal-scale estimates; everything else traces to the sources above. Trajectory chart pathways are stylized illustrations anchored to the published endpoint values.