Taiga is a boreal forest covered by conifers. See sections 1.5 and 4.3.3.
A Taylor series is the representation of a function as an infinite sum of terms. These terms are calculated from the values of the derivatives of the function at a single point. If the series is truncated to a finite number of terms, the resulting Taylor polynomial provides a polynomial approximation of the function around that point.
A teleconnection is usually indicated by the correlation between the values observed at two separate locations. This link is related to a pattern of variability, associated with wave propagation, the presence of mountains, etc. See section 5.2.
Thermal expansion is the change in the volume of a constant mass (e.g. of oceanic water) as a result of a change in its temperature. In the sea, a temperature increase produces an increase in the volume of water (also called dilation or dilatation) and thus a rise in sea levels if the oceanic mass remains unchanged.
A thermocline is a region in the ocean with a strong temperature gradient. Oceanographers usually make a distinction between the seasonal thermocline (which is formed at the base of the summer mixed layer) and the permanent thermocline (which separates the surface layer from the relatively homogenous deep ocean). See sections 1.3.3.1, 1.3.3.2 and 5.2.1.
The thermohaline circulation is a large-scale circulation in the ocean, which involves circulation at both the surface and at great depths. It is, at least partly, driven by the density contrasts in the ocean. See sections 1.3.2, 2.1.5.2 and 5.5.1 and see also Gulf Stream, deep water formation and water mass formation.
A timescale is related to the dominant periodicity of the phenomena of interest to an investigator. For instance, if someone is interested in variations on a seasonal timescale, the analysis will be mainly devoted on the differences between the various seasons. Timescales can also be daily, monthly, annual, decadal, centennial, millennial, etc.
The timescale of variation of a process represents the time over which significant variations of the processes can be expected to be observed. It takes millions of years for plate tectonics to induce movements of the continents that have a clear impact on the climate. This process is thus said to be important for climate on the timescale of millions of years. The timescale can represent an order of magnitude (see section 5.1) or be defined very precisely, for example, on the basis of spectral analysis (see section 5.4.1) or on an exponential decay (see Eq. 4.15).
The total solar irradiance is the radiant energy (i.e., the energy of electromagnetic waves) emitted by the Sun over all wavelengths, that falls each second on 1 square meter perpendicular to the Sun's rays at the mean Earth−Sun distance, measured outside the Earth's atmosphere. It measures the solar energy flux in W/m2, and is sometimes called solar constant. See sections 2.1.1 and 5.5.2.1.
A tracer is a constituent that is transported by a flow. A distinction is often made between active tracers that modify the flow through their influence on density (such as temperature and salinity in the ocean), and passive tracers that do not influence the motion (such as chlorofluorocarbons in the ocean). In oceanography, phytoplankton and zooplankton are generally treated as tracers because their movement is mainly determined by the ocean circulation. See section 3.3.5.
Trade winds are easterly winds (from the northeast in the Northern Hemisphere and the southeast in the Southern Hemisphere) characteristic of tropical regions. See sections 1.2.2, 1.3.2 and 5.2.1.
The transient climate response (TCR) is defined as the global average of the annual mean temperature change averaged over years 60 to 80 in an experiment in which the CO2 concentration is increased by 1% per year until year 70 (i.e. until it reaches double its initial value). See section 4.1.4.
Trophic levels are the various stages within food chains. Standard examples of trophic levels are the primary producers, the primary consumers (herbivores), and higher-level consumers (predators), as well as the decomposers that transform dead organisms and waste materials into nutrients available for the producers.
The tropopause is the boundary between the troposphere and the stratosphere located at an altitude of about 10 km. See sections 1.2.1, 4.1.1 and 4.1.3.
The troposphere is the lowest part of the Earth's atmosphere. Its average depth is about 10km. See sections 1.2.1 and 4.1.1.
The true longitude (λt) is the angle on the ecliptic plane between the position of the Earth relative to the Sun at any given time and at the vernal equinox. See sections 2.1.3.2 and 5.4.1.
In a numerical scheme using finite differences, the truncation error is the difference between the partial differential equation and the finite difference equation. See section 3.4.1.
The tundra is a biome, characteristic of regions where trees cannot grow because the temperature is too low. See sections 1.5, 4.3.3 and 5.4.2.