claim: The new research showed that [oxygen isotopes in foraminifera] can change
evidence: Stable isotopes of oxygen (δ18O) and carbon (δ13C) are recorded well in speleothems, giving high-resolution data that can show annual variation in temperature (oxygen isotopes primarily reflect rainfall temperature) and precipitation (carbon isotopes primarily reflect C3/C4 plant composition and plant productivity, but the interpretation is often complicated).