diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index aab1cacd52..3531be2432 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -45,6 +45,10 @@ repos:
     hooks:
       - id: flake8
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: 'v0.812'
+    rev: 'v0.990'
     hooks:
       - id: mypy
+        additional_dependencies:
+          - 'types-PyYAML'
+          - 'types-pkg_resources'
+          - 'types-requests'
diff --git a/environment.yml b/environment.yml
index c219e6a5a4..21795e34b2 100644
--- a/environment.yml
+++ b/environment.yml
@@ -14,6 +14,7 @@ dependencies:
   - esmpy!=8.1.0  # see github.com/ESMValGroup/ESMValCore/issues/1208
   - geopy
   - iris>=3.2.1
+  - mypy>=0.990
   - nested-lookup
   - netcdf4!=1.6.1  # github.com/ESMValGroup/ESMValCore/issues/1723
   - pandas
diff --git a/esmvalcore/_task.py b/esmvalcore/_task.py
index 7fc7bf893b..9e158408a0 100644
--- a/esmvalcore/_task.py
+++ b/esmvalcore/_task.py
@@ -15,6 +15,7 @@
 from multiprocessing import Pool
 from pathlib import Path, PosixPath
 from shutil import which
+from typing import Optional
 
 import psutil
 import yaml
@@ -709,7 +710,7 @@ def get_independent(self) -> 'TaskSet':
                 independent_tasks.add(task)
         return independent_tasks
 
-    def run(self, max_parallel_tasks: int = None) -> None:
+    def run(self, max_parallel_tasks: Optional[int] = None) -> None:
         """Run tasks.
 
         Parameters
diff --git a/esmvalcore/cmor/table.py b/esmvalcore/cmor/table.py
index e6a76c0767..f4db69f2a3 100644
--- a/esmvalcore/cmor/table.py
+++ b/esmvalcore/cmor/table.py
@@ -3,6 +3,8 @@
 Read variable information from CMOR 2 and CMOR 3 tables and make it
 easily available for the other components of ESMValTool
 """
+from __future__ import annotations
+
 import copy
 import errno
 import glob
diff --git a/esmvalcore/config/_config_validators.py b/esmvalcore/config/_config_validators.py
index 26990c49e7..63e33968d0 100644
--- a/esmvalcore/config/_config_validators.py
+++ b/esmvalcore/config/_config_validators.py
@@ -1,4 +1,6 @@
 """List of config validators."""
+from __future__ import annotations
+
 import logging
 import os.path
 import warnings
@@ -243,7 +245,7 @@ def validate_diagnostics(
     }
 
 
-def deprecate(func, variable, version: str = None):
+def deprecate(func, variable, version: Optional[str] = None):
     """Wrap function to mark variables to be deprecated.
 
     This will give a warning if the function will be/has been deprecated.
diff --git a/esmvalcore/config/_logging.py b/esmvalcore/config/_logging.py
index 0831618fe3..674fad953d 100644
--- a/esmvalcore/config/_logging.py
+++ b/esmvalcore/config/_logging.py
@@ -5,7 +5,7 @@
 import os
 import time
 from pathlib import Path
-from typing import Union
+from typing import Optional, Union
 
 import yaml
 
@@ -27,8 +27,10 @@ def _purge_file_handlers(cfg: dict) -> None:
     ]
 
 
-def _get_log_files(cfg: dict,
-                   output_dir: Union[os.PathLike, str] = None) -> list:
+def _get_log_files(
+    cfg: dict,
+    output_dir: Optional[Union[os.PathLike, str]] = None,
+) -> list:
     """Initialize log files for the file handlers."""
     log_files = []
 
@@ -59,9 +61,11 @@ def _update_stream_level(cfg: dict, level=None):
                 handler['level'] = level.upper()
 
 
-def configure_logging(cfg_file: Union[os.PathLike, str] = None,
-                      output_dir: Union[os.PathLike, str] = None,
-                      console_log_level: str = None) -> list:
+def configure_logging(
+    cfg_file: Optional[Union[os.PathLike, str]] = None,
+    output_dir: Optional[Union[os.PathLike, str]] = None,
+    console_log_level: Optional[str] = None,
+) -> list:
     """Configure logging.
 
     Parameters
diff --git a/esmvalcore/experimental/recipe.py b/esmvalcore/experimental/recipe.py
index c237164ed6..eb68d58655 100644
--- a/esmvalcore/experimental/recipe.py
+++ b/esmvalcore/experimental/recipe.py
@@ -100,7 +100,11 @@ def _load(self, session: Session) -> RecipeEngine:
                             config_user=config_user,
                             recipe_file=self.path)
 
-    def run(self, task: str = None, session: Session = None):
+    def run(
+        self,
+        task: Optional[str] = None,
+        session: Optional[Session] = None,
+    ):
         """Run the recipe.
 
         This function loads the recipe into the ESMValCore recipe format
diff --git a/esmvalcore/experimental/recipe_metadata.py b/esmvalcore/experimental/recipe_metadata.py
index e8842a5fe2..1801e92ca2 100644
--- a/esmvalcore/experimental/recipe_metadata.py
+++ b/esmvalcore/experimental/recipe_metadata.py
@@ -1,5 +1,7 @@
 """API for recipe metadata."""
 
+from typing import Optional
+
 import pybtex
 from pybtex.database.input import bibtex
 
@@ -23,7 +25,7 @@ class Contributor:
         ORCID url
     """
 
-    def __init__(self, name: str, institute: str, orcid: str = None):
+    def __init__(self, name: str, institute: str, orcid: Optional[str] = None):
         self.name = name
         self.institute = institute
         self.orcid = orcid
diff --git a/esmvalcore/experimental/recipe_output.py b/esmvalcore/experimental/recipe_output.py
index 7ed357595b..40de3150f5 100644
--- a/esmvalcore/experimental/recipe_output.py
+++ b/esmvalcore/experimental/recipe_output.py
@@ -255,7 +255,7 @@ class OutputFile():
 
     kind: Optional[str] = None
 
-    def __init__(self, path: str, attributes: dict = None):
+    def __init__(self, path: str, attributes: Optional[dict] = None):
         if not attributes:
             attributes = {}
 
@@ -291,7 +291,7 @@ def references(self) -> tuple:
             self._references = tuple(Reference.from_tag(tag) for tag in tags)
         return self._references
 
-    def _get_derived_path(self, append: str, suffix: str = None):
+    def _get_derived_path(self, append: str, suffix: Optional[str] = None):
         """Return path of related files.
 
         Parameters
@@ -325,7 +325,12 @@ def provenance_xml_file(self):
         return self._get_derived_path('_provenance', '.xml')
 
     @classmethod
-    def create(cls, path: str, attributes: dict = None) -> 'OutputFile':
+    def create(
+        cls,
+        path: str,
+        attributes:
+        Optional[dict] = None,
+    ) -> 'OutputFile':
         """Construct new instances of OutputFile.
 
         Chooses a derived class if suitable.
diff --git a/esmvalcore/experimental/utils.py b/esmvalcore/experimental/utils.py
index 2926053dee..3c2b1f003a 100644
--- a/esmvalcore/experimental/utils.py
+++ b/esmvalcore/experimental/utils.py
@@ -3,7 +3,7 @@
 import os
 import re
 from pathlib import Path
-from typing import Pattern, Tuple, Union
+from typing import Optional, Pattern, Tuple, Union
 
 from esmvalcore.config._diagnostics import DIAGNOSTICS
 
@@ -41,7 +41,7 @@ def find(self, query: Pattern[str]):
         return matches
 
 
-def get_all_recipes(subdir: str = None) -> list:
+def get_all_recipes(subdir: Optional[str] = None) -> list:
     """Return a list of all available recipes.
 
     Parameters
diff --git a/setup.cfg b/setup.cfg
index 88fee9d4fc..6ea564b2a6 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -34,7 +34,6 @@ include_trailing_comma = true
 
 [mypy]
 # see mypy.readthedocs.io/en/stable/command_line.html
-implicit_optional = True
 ignore_missing_imports = True
 files = esmvalcore, tests
 
diff --git a/setup.py b/setup.py
index 528d34d0d7..25e996e274 100755
--- a/setup.py
+++ b/setup.py
@@ -70,6 +70,7 @@
         'pytest-xdist',
         'ESMValTool_sample_data==0.0.3',
         # MyPy library stubs
+        'mypy>=0.990',
         'types-requests',
         'types-pkg_resources',
         'types-PyYAML',
diff --git a/tests/sample_data/multimodel_statistics/test_multimodel.py b/tests/sample_data/multimodel_statistics/test_multimodel.py
index 485328d85b..480169dc61 100644
--- a/tests/sample_data/multimodel_statistics/test_multimodel.py
+++ b/tests/sample_data/multimodel_statistics/test_multimodel.py
@@ -4,6 +4,7 @@
 import platform
 from itertools import groupby
 from pathlib import Path
+from typing import Optional
 
 import iris
 import numpy as np
@@ -69,7 +70,7 @@ def fix_metadata(cubes):
         cube.coord('air_pressure').bounds = None
 
 
-def preprocess_data(cubes, time_slice: dict = None):
+def preprocess_data(cubes, time_slice: Optional[dict] = None):
     """Regrid the data to the first cube and optional time-slicing."""
     # Increase TEST_REVISION anytime you make changes to this function.
     if time_slice:
@@ -92,7 +93,8 @@ def get_cache_key(value):
     """Get a cache key that is hopefully unique enough for unpickling.
 
     If this doesn't avoid problems with unpickling the cached data,
-    manually clean the pytest cache with the command `pytest --cache-clear`.
+    manually clean the pytest cache with the command `pytest --cache-
+    clear`.
     """
     py_version = platform.python_version()
     return (f'{value}_iris-{iris.__version__}_'