Quick Answer
At 90% of its current distance from the Sun, Earth would receive about 23% more solar energy because sunlight follows an inverse-square relationship. The climate would warm substantially, but the exact temperature change would depend on feedbacks involving clouds, water vapor, ice and oceans. Earth’s orbital year would also become shorter.
Earth’s distance from the Sun controls how much solar energy reaches the planet. A 10% reduction in distance is therefore a large climatic change.
More sunlight
Solar flux scales with the inverse square of distance. Moving to 0.9 astronomical units would increase incoming solar energy by roughly 1/0.9², or about 23%.
The climate responds nonlinearly
A warmer planet would hold more water vapor, while ice and snow would shrink. Clouds could amplify or counteract some of the warming, making the final temperature difficult to calculate without a climate model.
The year gets shorter
Closer orbits around the Sun have shorter orbital periods. Earth’s year would therefore become shorter if its new orbit were stable.
Could life survive?
Many organisms could potentially adapt over evolutionary timescales, but ecosystems and agriculture would face major stress during a rapid transition.
Established scienceThe 23% increase in solar flux follows directly from the inverse-square law. The resulting global temperature is much less direct because climate feedbacks matter.
The bottom line
Moving Earth 10% closer would be a major climate experiment, not an instant end of life. The extra sunlight would push the climate toward a warmer equilibrium and shorten the year.
A note on our approach: Every article on WhatIfLab separates what current science establishes from what remains genuinely speculative. Where we cite a figure or finding, it reflects published, mainstream research at the time of writing — not a prediction dressed up as fact.