---
watermark: ORIRO
disable-model-invocation: true
name: sci-climate
provider: ORIRO.ai
copyright: Copyright (c) 2026 ORIRO.ai
description: >





  Climate science — the climate system, greenhouse effect, climate change evidence, impacts, and mitigation and adaptation strategies.

  Sources: OpenStax textbooks (CC-BY), Khan Academy, MIT OCW, NOAA, IPCC reports.
---

# Climate Science

## The climate system

Five components interact to determine climate:
**Atmosphere:** Thin layer of gases. Weather happens here. Greenhouse gases trap heat.
**Hydrosphere:** Oceans, lakes, rivers, groundwater. Oceans absorb 90%+ of excess heat and 25% of CO₂.
**Cryosphere:** Ice sheets, glaciers, sea ice, permafrost. High albedo reflects sunlight.
**Biosphere:** All living things. Absorb and release carbon, affect albedo.
**Geosphere:** Land surface. Soil carbon, volcanism, weathering.

## The greenhouse effect

Solar radiation passes through atmosphere → Earth absorbs and warms → Earth emits infrared (heat) radiation → Greenhouse gases (CO₂, CH₄, N₂O, H₂O, O₃) absorb IR and re-emit in all directions → Earth warms more than it would without atmosphere.
Natural greenhouse effect is essential for life. Enhanced greenhouse effect from human emissions is causing warming.

**Key greenhouse gases:**
CO₂: 76% of anthropogenic GHG. Fossil fuels, deforestation. Long atmospheric lifetime (centuries).
CH₄ (Methane): 16%. Agriculture (livestock, rice), natural gas, landfills. 80× more potent than CO₂ over 20 years but shorter lifetime.
N₂O: 6%. Agriculture (fertilizers). ~270× CO₂ over 100 years.
F-gases: Industrial. Very high GWP (global warming potential).

## Evidence for human-caused climate change

**Temperature:** Global surface temperature has risen ~1.2°C since pre-industrial times (IPCC AR6, 2021). Warming accelerating. 2015-2023: hottest years on record.
**CO₂:** Atmospheric CO₂ was ~280 ppm pre-industrial. Now >420 ppm — highest in at least 3 million years. Rise directly tracks industrial emissions.
**Ice cores:** Bubbles in ancient ice contain ancient air. CO₂ and temperature correlated over 800,000 years of records. Current CO₂ rise unprecedented in rate.
**Isotopic signature:** Human-emitted CO₂ has distinct carbon isotope ratio (lighter C-12 from fossil fuels) — measurable fingerprint.
**Attribution:** Statistical methods can attribute specific extreme events to climate change. Human influence now detectably affects virtually all regions.

## Observed impacts (current and near-term)

Sea level rise: ~20 cm since 1900; accelerating. Thermal expansion + ice melt.
Ocean acidification: pH dropped 0.1 units (30% more acidic). CO₂ + water → carbonic acid.
Extreme weather: Heat waves, extreme precipitation, drought, tropical cyclone intensity all increasing.
Arctic amplification: Arctic warming 3× faster than global average. Sea ice extent at record lows.
Ecosystem shifts: Species moving poleward and upslope. Coral bleaching increasing.

## Mitigation strategies

**Decarbonize electricity:** Solar and wind now cheapest sources of new generation in most of the world. Storage improving rapidly.
**Electrify everything:** EVs, heat pumps, electric industrial processes. Works when grid is clean.
**Energy efficiency:** Cheapest unit of energy is the one not used.
**Land use:** Halting deforestation + reforestation + agricultural soil management.
**Methane reduction:** Faster near-term impact than CO₂.
**Carbon removal:** Direct air capture, bioenergy with carbon capture, enhanced weathering. Currently expensive and limited scale.

## Carbon budgets

To limit warming to 1.5°C with 50% probability: ~500 GtCO₂ remaining from 2020.
At current ~40 GtCO₂/year emissions: budget exhausted in ~12 years from 2020.
For 2°C with 67% probability: ~1,150 GtCO₂ remaining from 2020.

Sources: IPCC AR6 (2021-2022, free public access at ipcc.ch), NOAA (noaa.gov),
NASA climate portal (climate.nasa.gov), Carbon Brief (free, evidence-based)