When Will We Pass 1.5°C? The Latest 2024 Data

Short answer

Scientists expect the world to temporarily exceed 1.5°C above pre-industrial temperatures within the next few years and to pass it permanently likely in the early 2030s if current emissions continue. Key reports from the World Meteorological Organization (WMO) and the IPCC, plus AI-based forecasts, point to the same broad timeline with varying odds.

When will we cross 1.5°C?

Temporary versus long-term crossing

Scientists use different measures: single years, five-year averages, and long-term averages (many decades). A temporary exceedance means one year or a short run above 1.5°C. A permanent crossing means the long-term average stays above 1.5°C for decades.

What the latest reports say

• The WMO 2024 forecast gives about a 70% chance that the five-year average for 2025–2029 will be above 1.5°C. It also estimates the 20-year average for 2015–2034 at about 1.44°C (90% range 1.22–1.54°C).
• The IPCC has said that under current national pledges the world is likely to surpass 1.5°C in the coming decades unless very large, rapid cuts in emissions happen.
• An AI-based study adds that crossing 1.5°C in the 2030s is plausible and that even aggressive reductions still carry a high chance of passing the threshold for the long term.

Why there is uncertainty

• Natural ups and downs: weather patterns like El Niño can push short-term temperatures higher.
• Different measurements: year-to-year highs differ from multi-decade averages.
• Future emissions: strong cuts delay or limit long-term warming; continued high emissions speed it up.

Simple timeline summary

1. Now to 2027: high chance of temporary years above 1.5°C (WMO and UN outlooks). See the UN climate reports.
2. 2025–2029: WMO gives a ~70% chance the five-year average will exceed 1.5°C.
3. Early to mid-2030s: many models and analyses (including AI studies and IPCC scenarios) show a likely permanent crossing unless rapid global cuts occur.

What changes at 1.5°C—one clear data point and its meaning

Data point: the WMO found the 20-year central estimate for 2015–2034 is 1.44°C (90% range 1.22–1.54°C). Practical implication: even small extra warming raises the odds of extreme heat, heavy rainfall, and sea level rise. That means cities, farms, and coastlines should plan now for more frequent heatwaves and flooding.

Impacts: 1.5°C versus 2.0°C

The IPCC and other reports show clear differences between 1.5°C and 2°C. Below is a compact comparison.

Impact	~1.5°C	~2.0°C
Heat extremes	Fewer extreme heat days, but large increases vs pre-industrial	Much more frequent and intense heatwaves
Sea level rise	Projected global sea level rise lower by ~0.1 m by 2100 vs 2°C	Higher sea level, more coastal flooding
Biodiversity	Less habitat loss than 2°C; many species still at risk	Much higher risk of species loss and ecosystem collapse
Food & water	Increased drought and flood risks in some regions	More severe impacts on crops and water supply

Regional notes

Warming is uneven. The Arctic is warming several times faster than the global average. The WMO predicts Arctic winter warming of about 2.4°C above the 1991–2020 baseline for the next five extended winters, which means big changes for ice and wildlife. Coastal regions face higher sea level rise and storm surge risks, as summarized by NOAA.

How experts make these forecasts

Scientists use climate models, historical observations, and statistical tools. Examples include:

• Global climate models run with different greenhouse gas paths (NOAA / CMIP).
• Decadal forecasts that blend model output with recent observations (WMO).
• New AI-based methods that learn from model ensembles and observations to estimate timing.

What this means for planning

Whether temporary or permanent, higher odds of 1.5°C matter for decisions today.

• For cities: ramp up heat action plans, cooling centers, and flood defenses.
• For farmers: plan for new planting windows, drought-tolerant crops, and water management.
• For businesses and insurers: factor higher frequency of extreme events into risk models and pricing.

How you can use these projections

1. Trust the trend: treat the chance of near-term 1.5°C years as real and plan for heat and floods.
2. Support emissions cuts: deep, fast cuts reduce long-term risk of staying above 1.5°C.
3. Prepare locally: ask local leaders about heat and flood plans, and update home insurance and emergency kits.

Key sources and where to read more

• WMO 2024 decadal and five-year predictions
• IPCC Special Report on 1.5°C
• Stanford AI forecast summary
• UN climate reports and updates
• Climate Action Tracker 2024 update
• NASA: Effects of Climate Change
• NOAA coastal impacts

FAQs

Will 1.5°C be passed forever?

Not necessarily right away. Short-term years can go above 1.5°C because of natural variability. But most models show a high chance the long-term average will pass 1.5°C in the 2030s unless emissions fall fast.

Can we avoid 2°C?

It is still possible to limit warming to well below 2°C, but it requires quick and deep cuts in greenhouse gas emissions worldwide, far beyond current pledges. The IPCC lays out how much faster cuts must be.

What is the pre-industrial baseline?

Most reports use the period 1850–1900 as the pre-industrial baseline. Temperatures are compared to that time to measure global warming since the industrial era.

Bottom line

Multiple top sources agree: near-term years above 1.5°C are likely and a permanent crossing in the early 2030s is plausible if emissions do not drop fast. That means more heat, more heavy rain, and rising seas are likely to become normal. Use the forecasts to plan, and support policies and actions that cut emissions now.